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Me ctiani c s De ID t . 



The Penton Publishing Co. 

Cleveland, O., U. S. A. 
Publishers of 

The Foundry The Iron Trade Review 
Marine Review Daily Metal Trade 

Power Boating Abrasive Industry 



AMERICAN 

MALLEABLE 

CAST IRON 



By H. A. Schwartz 



First Edition 



Published by 

The Penton Publishing Co. 

Cleveland, Ohio 

1922 



Library 



Copyright in the United States 

and 
Entered at Stationers' Hall, London 

1922 

The Penton Publishing Co. 
Cleveland, Ohio 



THE PENTON PRESS CO., CLEVELAND 



THE MEMORY OF 

ALLEN SMITH BIXBY 

Wi:OSE INSTRUCTION, CO-OPERATION AND ADVICE I OWE THE EARLY 
OPPORTUNITIES WHICH MADE THIS BOOK POSSIBLE 
IT IS AFFECTIONATELY DEDICATED 



588565 



PREFACE 

THE literature of malleable cast iron, in the American sense 
of that term, is limited to a single book first issued about 
10 years ago and now out of print, and to a series of articles 
of great diversity of character and quality in the technical publi- 
cations of this country and Europe. Much of the most valuable 
scientific matter is buried in the purely scientific press, frequently 
under titles which do not suggest its application to any one 
not a specialist in metallurgy. 

Under these circumstances the preparation of a new book 
dealing with American malleable cast iron in theory and 
practice may serve a useful purpose as summarizing and rec- 
ording, so far as any book can, the contemporary state of the 
art in the metallurgy of this product. 

If in the following pages the specialist finds much which ap- 
pears to him elemental or trivial or the non technical reader finds 
matter which appears too complex, the author must plead in ex- 
tenuation his desire to prepare a book to suit many kinds of 
readers. 

This has necessitated the inclusion of much elementary 
matter both in metallurgy and mechanics which will be useful 
only in acquainting -the lay reader with the interpretation of 
terms and data which form the every day vocabulary of the 
technician. 

On the other hand it has seemed that in order that the 
reader might secure full value from a reading of these 
pages no known fact or theory should be excluded merely in the 
interest of simplicity. 

Feeling that no single individual is justified in the belief that 
his own views are final in so complex a subject the author 
has not hesitated to refer freely to the literature and even to 
record opinions contrary to his own. So far as possible due 
credit has been given in all such cases. 

Guided by the injunction of Leonardo da Vinci, "Con- 
firm your statements by examples and not by assertions", it has 

VII 



been the author's constant effort to- record facts rather than 
opinions wherever possible. This has been particularly true 
in the chapters dealing with manufacturing methods. In these 
chapters the record is one of what has been rather than of what 
might be accomplished. Much of the experimental work re- 
ferred to is the work of the author's associates. In this connec- 
tion special recognition must be given to the very unusual micro- 
graphs which are the work of Harrie R. Payne, chief chemist 
and metallographer of the author's laboratory. 

Many of the author's friends within the malleable industry, 
in the organization of which he has the honor to be a member, 
and among the business connections of that association have 
contributed valuable information. 

Whenever possible credit has been assigned. In some cases 
where for obvious reasons it was- improper to identify the in- 
formation the latter has consented to the anonymous presenta- 
tion of his material. The co-operation of the American Malle- 
able Castings Association in furnishing statistics and of the 
late Thos. Devlin of Philadelphia, and Alfred E. Hammer, 
Branford, Conn., in contributing historic matter from their long 
experience is especially worthy of grateful acknowledgment. 

If the following pages contain any information calculated 
to dispel the many misconceptions as to malleable cast iron and 
to acquaint the interested reader accurately with the proper- 
ties and methods of manufacture of this interesting, valuable and 
characteristically American product, the author's labor will 
have been richly repaid. 

H. A. SCHWARTZ 



VIII 



CONTENTS 

CHAPTER I 
Early History of Ironmaking 1 

CHAPTER II 

Development of Malleable Industry in the United States 15 

CHAPTER III 
Metallurgy of Malleable Iron 41 

CHAPTER IV 

General Manufacturing and Plant 71 

CHAPTER V 

Melting Stock 91 

CHAPTER VI 

Fuel and Refractories 109 

CHAPTER VII 

Air Furnace Melting 135 

CHAPTER VIII 

Electric Furnace Melting 159 

CHAPTER IX 

Cupola and Open-hearth Melting 175 

CHAPTER X 

Annealing Practice 189 

CHAPTER XI 

Principles of Annealing 213 

CHAPTER XII 

Molding and Patternmaking .* 233 

CHAPTER XIII 

Cleaning and Finishing 249 

CHAPTER XIV 

Inspecting and Testing " 267 

CHAPTER XV 

Tensile Properties 287 

CHAPTER XVI 
Compression, Bending and Shear 303 

CHAPTER. XVII 
Fatigue, Impact, Hardness and Wear 315 

CHAPTER XVIII 
Plastic Deformation 339 

CHAPTER XIX 

Thermal and Electrical Properties 371 

Selected Bibliography 385 

Index 403 

IX 



LIST OF ILLUSTRATIONS 

PAGE 
Fig. 1 A meteorite - in the American Museum of Natural History, 

New York, brought from Greenland by Admiral Peary 2 

Fig. 2 A primitive furnace, 1500 B. C. The illustration was re- 
produced from an Egyptian wall painting 

Fig. 3 One of the earliest blast furnaces 4 

Fig. 4 An early American blast furnace 7 

Fig. 5 Reaumur's foundry in 1724. One furnace has just been 

emptied and the blast is being applied to the other 

Fig. 6 Statue of Seth Boyden, erected in the city park of Newark, 
N. J M by citizens in memory of the man who laid the founda- 
tion for the malleable industry in the United States 12 

Fig. 7 Seth Boyden 16 

Fig. 8 J. H. Barlow, Boyden's successor 16 

Fig. 9 Distribution of malleable iron foundries in the United 
States. The dots represent the location of malleable foundries 

according to data compiled for government use : . . . . 20 

Fig. 10 Map showing location of principle sellers of malleable iron 

castings in the United States 22 

Fig. 11 Comparison of production of steel and malleable iron 

castings 24 

Fig. 12 Familiar figures in the development of the malleable in- 
dustry in the United States 28 

Fig. 13 Three metallurgists who have been closely identified with 

the technical advancement of the industry 32 

Fig. 14 The names of these men are linked with the rise of the 

American malleable industry 34 

Fig. 15 Austenite and ledeburite in manganiferous white cast iron 42 

Fig. 16 Martensite in quenched white cast iron 42 

Fig. 17 Troostite in steel 43 

Fig. 18 Pearlite in incompletely annealed malleable 43 

Fig. 19 Spheroidized pearlite 44 

Fig. 20 Graphite in gray iron 44 

Fig. 21 Soft gray cast iron 45 

Fig. 22 Malleable cast iron 45 

Fig. 23 Benedict's diagram recording the equilibrium conditions in 
terms of temperature and agraphic (non graphitic) carbon. 

It is based on Benedict's principle, somewhat modified 47 

Fig. 24 A further modification of Benedict's diagram indicating 

the results of recent research work 51 

Fig. 25 Graphite crystals in malleable made from hard iron con- 
taining graphite 54 

Fig. 26 Unannealed hard iron. The structure is always dendritic 

but varies slightly with the carbon content 55 

XI 



LIST OF ILLUSTRATIONS Continued 

PAGE 

Fig. 27 Effect of silicon in relation to carbon on malleable. This 

graph is based on data from Thrasher's determinations 56 

Fig. 28 Beginning of graphitization after one half hour at 1700 

degrees Fahr 58 

Fig. 29 Progress of graphitization after \ l / 2 hours at 1700 degrees 

Fahr 58 

Fig. 30 Progress of graphitization after 3 l / 2 hours at 1700 de- 
grees Fahr 60 

Fig. 31 Equilibrium at 1700 degrees Fahr. after 70 hours 60 

Fig. 32 Imperfect attainment of equilibrium below A due to too 

short a time 62 

Fig. 33 Normal malleable iron, metastable equilibrium below A t . . 62 

Fig. 34 Graphite crystals produced by annealing at 2100 degrees 

Fahr , 64 

Fig. 35 Manganese sulphide in a malleable cast iron. The arrows 

point to MnS 64 

Fig. 36 Chart showing conversion of combined carbon into temper 

carbon 66 

Fig. 37 Changes of metallographic composition during the freezing 

and annealing of white iron 69 

Fig. 38 Organization chart for malleable foundry 72 

Fig. 39 A good example of the approved style of architecture for 

a malleable foundry built a generation ago 74 

Fig. 40 Exterior view of a large malleable plant built about 1917 76 

Fig. 41 Coreroom of a modern malleable plant showing roof con- 
struction designed to facilitate removal of fumes and gases 
and to afford good natural lighting 78 

Fig. 42 Interior of the annealing department of a modern 

malleable foundry 80 

Fig. 43 Chart showing cycle of principal operations in a malle- 
able plant 83 

Fig. 44 Chart showing division of labor in a typical foundry .... 84 

Fig. 45 Molding floor in a well organized American malleable 

foundry 86 

Fig. 45 The stock yard usually is served by a traveling crane 92 

Fig. 47 Map showing location of principal ore fields, and coke and 

charcoal blast furnace producing malleable pig iron 95 

Fig. 48 An open pit iron ore mine on the Mesabi range. Ores in 

this district are suitable for making malleable pig 98 

Fig. 49 An ore loading dock at one of the ports on Lake 

Superior 100 

XII 



LIST OF ILLUSTRATIONS Continued 

PAGE 
Fig. 50 An ore unloading dock at a Lake Erie port, where the 

ore is transferred from ore carrier to railroad car 102 

Fig. 51 A charcoal blast furnace in Michigan where malleable pig 

iron is made 104 

Fig. 52 A typical coke blast furnace in the Mahoning valley 106 

Fig. 53 Map showing location of principal resources of metallurgi- 
cal fuel in the United States .' 110 

Fig. 54 A modern coal tipple in West Virginia 112 

Fig. 55 Picking table in a coal tipple showing facilities for remov- 
ing slate, sulphur, etc., by hand 114 

Fig. 56 Adjustable loading boom which places coal in car without 

breakage 114 

Fig. 57 A modern by-product coke plant which is engaged in 

making foundry fuel 116 

Fig. 58 A typical scene at a beehive coke oven plant in- the Con- 

nellsville region 118 

Fig. 59 Cross section of a modern gas producer 120 

Fig. 60 A scene in an important oil field in Oklahoma 122 

Fig. 61 Operations in a molding sand pit 125 

Fig. 62 Hauling sand from a pit 125 

Fig. 63 Map showing the principal sources of molding sand, fire- 
clay and brick in the United States 126 

Fig. 64 Open fireclay pit covering over 10 acres and with bed 

of clay from 25 to 40 feet thick '. 128 

Fig. 65 A plant in Missouri showing round, down-draft kilns, 

factory and stock sheds 130 

Fig. 66 A repress room in a Missouri firebrick plant, showing 

machines in which stiff mud firebrick are made 132 

Fig. 67 Firebrick and special fireclay shapes in kiln ready to be 

burned 133 

Fig. 68 Sectional drawings showing construction of typical air 

furnace 136 

Fig. 69 Graph showing recombination of carbon in pig iron,... 139 
Fig. 70 The roof of the modern air furnace is almost straight.. 140 
Fig. 71 A waste heat boiler connected to two air furnaces. Note 

that coal for auxiliary firing is on hand 142 

Fig. 72 Gray sprue 148 

Fig. 73 Gray sprue showing white patches. Characteristic of less 

but still excessive carbon and silicon 148 

Fig. 74 Moderately mottled sprue characteristic of carbon, silicon 

and temperature suited to very small work 148 

XIII 



LIST OF ILLUSTRATIONS Continued 

PAGE 
Fig. 75 Normal sprue for metal of the higher carbon ranges of 

specification metal in average work 149 

Fig. 76 Similar to Fig. 74 but lower in carbon 149 

Fig. 77 Similar to Fig. 76 but quite low carbon 149 

Fig. 78 ''High" iron i.e. metal low in carbon, silicon and man- 
ganese. Fracture granular throughout and edge showing blow- 
holes 149 

Fig. 79 Changes of metal after tapping 151 

Fig. 80 A powdered coal atatchment for an air furnace 155 

Fig. 81 Cupola producing molten iron the starting point of the 

Kranz triplex process 160 

Fig. 82 Two-ton side-blow converter producing liquid steel from 

cupola metal in triplex process 162 

Fig. 83. Transfer train consisting of electric motor car and 
trailer with' crane ladle. This equipment is used in carrying 

cupola and converter metal to the electric furnaces 165 

Fig. 84 Heroult electric furnace in which cupola and converter 

metal is charged for final step in triplex process 168 

Fig. 85 Heroult furnace tilted for pouring 170 

Fig. 86 Pouring side of open-hearth furnace for malleable iron.. 176 
Fig. 87 Charging side of open-hearth furnace in malleable plant . . 178 
Fig. 88 Design of a modern, stationary open-hearth steel furnace. 180-181 
Fig. 89 Separator plate designed to eliminate use of packing 

with annealing pots 190 

Fig. 90 A view of the annealing department in a modern malleable 

castings plant 194 

Fig. 91 Charging trucks facilitate the handling of pots to and 

from the annealing furnaces 195 

Fig. 92 The interior of the powdered coal mill of a modern malle- 
able plant 197 

Fig. 93 While most of the plants in the United States employ 
annealing furnaces similar to those shown in Fig. 90, a few 

plants use the pit type, illustrated above 198 

Fig. 94 Diagram showing the distribution of heat in a continuous- 
type annealing furnace 200 

Fig. 95 Interior of continuous-type annealing furnace looking 

toward the entrance end 200 

Fig. 96 Single section of combustion chamber of continuous type 

annealing furnace 201 

Fig. 97 A sectional plan and elevation of a double-chamber, car- 
type tunnel kiln for annealing malleable iron castings. The fir- 

XIV 



LIST OF ILLUSTRATIONS Continued 

PAGE 
ing zones are diagonally opposite each other 202 

Fig. 98 Rim of a casting containing most of the usual defects 
due to annealing. Etched with picric acid, magnified 100 diam- ' 
eters and subsequently reduced one-fourth on erfgraving ....216,217 

Fig. 99 Increase in carbon content at increasing depths below' the 

surface of malleable cast iron .........'... 223 

Fig. 100 Graph showing effect of removing one-sixteenth inch, 
decarborized surface in specimens of various diameters on the 
tensile properties of the metal 225 

Fig. 101 Graph showing effect of varying degrees of decarburi- 

zation on tensile properties of malleable cast iron 226 

Fig. 102 Equilibrium curves illustrating the reactions between car- 
bon, iron and oxygen, after the data of Matsubara 230 

Fig. 103 Methods of mounting patterns 234 

Fig. 104 Squeezer-type molding machine and mold and pattern 

equipment in place 236 

Fig. 105 Stripper and rollover -type molding machines 238 

Fig. 106 Curve showing contraction in cooling from solidification 

to room temperature 238 

Fig. 107 Graph showing the per cent of contraction of malleable 

from pattern size 240 

Fig. 108 Graphs showing relation of annealing upon the density 

of the metal 241 

Fig. 109 Casting with thin disk and thick hub, showing probable 

point of rupture 242 

Fig. 1-10 Type of casting with thin disk center and thick rim.. 242 

Fig. Ill Dendrite (about half size) from shrink in hard iron 
ingot 8 inches in . diameter by 20 inches high which was 
poured without feeding 244 

Fig. 112 Typical gate for malleable castings showing strainer, core 
and skimmer gates for furnishing clean metal for feeders and 
producing sound castings 246 

Fig. 113 Tumbling barrels are used for cleaning castings 250 

Fig. 114 Sand blast equipment is used for removing sand from 

castings 252 

Fig. 115 Sorting and inspecting small castings are important opera- 
tions in many plants 252 

Fig. 116 When machine center and casting center are not concen- 
tric apparent hard spots may be found .-...- 255 

Fig. 117 (left) Cementite persisting near a shrink. The metal in 

porous areas is somewhat oxidized 257 

XV 



LIST OF ILLUSTRATIONS Continued 

PAGE 

Fig. 118 (Right) Hard slag inclusions just below the surface 

which may dull cutting tools rapidly 257 

Fig. 119 Malleable casting effectively arc welded with Swedish iron. 
The changes visible microscopically were insufficient to make 
notable difference in metal. Area A is soft iron but very slightly 
recarburized from the malleable; B is an oxide or slag film, 
and C is the malleable showing but little resolution of carbon 

due to close confinement 258, 259 

Fig. 120 Hard iron casting successfully acetylene welded with hard 
iron and then annealed. Note metallurgical homogeneity of 
casting except for presence of slag. A is the original casting, 
B the slag, C the material of weld as noted by larger grain 
size, and D the material of weld as noted by persistence of a 

little pearlite due to decarburization 258, 259 

Fig. 121 Ineffective hard weld of malleable casting using ingot 
iron wire and acetylene method. Neither material has its 
original structure. A is the soft iron filler converted into hard 
iron by migration of carbon from the malleable. B is the 
original malleable iron, the background of which has become 
sorbitic due to recombination of carbon at temperature the 

metal reached in welding 258, 259 

Fig. 122 Photomicrograph showing heavy pearlitic rim which may 

cause machining difficulties 262 

Fig. 123 (Left) An effective acetylene weld, malleable becoming 
sorbitic due to resolution of carbon. A is gray iron converted 

into white cast iron by remelting. B is malleable 263 

Fig. 124 (Right) Tobin bronze weld in malleable. Note absence 
of oxides and slag in weld and absence of recombination of 
carbon due to relatively low melting point of breeze. A is . 

bronze, B is malleable 263 

Fig. 125 Analytical laboratory in malleable plant 268 

Fig. 126 Apparatus for determining carbon 269 

Fig. 127 Inverted types of metallographic microscope 272 

Fig. 128 Detail of inverted type of metallographic microscope 

(Bausch & Lomb) 272 

Fig. 129 A. S. T. M. tension test specimen 274 

Fig. 130 Dimensions of proposed tension test bar 276 

Fig. 131 A 200,000-pound Olsen universal testing machine 278 

Fig. 132 Ewing-type extensometer for determining elongation under 

load ...".... 279 

Fig. 133 Olsen-type torsion testing machine 280 

Fig. 134 Leeds & Northrup Co. apparatus for determining critical 

XVI 



LIST OF ILLUSTRATIONS Continued 

PAGE 

points by Roberts-Austin method 281 

Fig. 135 Apparatus for measuring magnetic properties of metal.. 281 

Fig. 136 Farmer fatigue testing machine 282 

Fig. 137 Charpy hammer for impact tests 283 

Fig. 138 Brinell hardness tester 284 

Fig. 139 Stress-strain diagram of malleable cast iron in tension 289 
Fig. 140 Tensile strength and elongation plotted from specimens 
submitted by members of American Malleable Castings As- 
sociation 291 

Fig. 141 Effect of carbon on tensile properties of malleable iron.. 293 
Fig. 142 Relation between tensile strength and elongation of malle- 
able cast iron 295 

Fig. 143 Comparison of tensile properties of machined and cast 

specimens of equal diameters 296 

Fig. 144 Results of tests on specimens not machined 298 

Fig. 145 V groove in bar 300 

Fig. 146 Necked specimens of steel (left) and malleable (right) 301 
Fig. 147 Stress strain diagram of malleable cast iron in com- 
pression 304 

Fig. 148 Malleable (center) and cast iron (right) in compression 
each specimen before testing was of the size and shape shown 

at the left 305 

Fig. 149 Diagram of stresses in cross bending of malleable iron 308 
Fig. 150 Displacement of planes by linear shear and (at right) by 

torsional shear 310 

Fig. 151 Stress strain diagram of malleable cast iron in torsion.... 311 
Fig. 152 Diagram showing factors to be considered in deter- 
mining torsion stresses 312 

Fig. 153 Effect of elongation of specimen on the resistance to 

dynamic tensile loads 319 

Fig. 154 Walker test wedges 321 

Fig. 155 Behavior of malleable iron under fatigue as a rotating 

beam 322 

Fig. 156 Separation of grains by repeated cross bendings 323 

Fig. 157 Relation between Brinell number and strength of malleable 

iron specimens 325 

Fig. 158 Graph showing comparison of Brinell and Shore numbers 

indicating relation between them is not definite 326 

Fig. 159 Tests of machining properties of malleable cast iron 330 

Fig. 160 Graph showing values of a in drilling formula 332 

XVII 



LIST OF ILLUSTRATIONS Continued 

PAGE 

Fig. 161 Graph showing values of'fc in drilling formula 333 

Fig. 162 Relation of torque and thrust to ultimate strength 334 

Fig. 163 Relation of torque and thrust to Brinell number 335 

Fig. 164 Slip bands in ferrite of malleable iron 341 

Fig. 165 Intragranular fracture of a ferrite grain in malleable.. 342 

Fig. 166 Intergranular failure of malleable 343 

Fig. 167 Ferrite grains in malleable, showing slip in two planes 

at right angles 344 

Fig. 168 Slip bands due to plastic compression in malleable iron 345 

Fig. 169 Plastic deformation of malleable in compression 345 

Fig. 170. Same specimen as shown in Fig. 169 347 

Fig. 171 Path of cross bending rupture through malleable 348 

Fig. 172 Malleable iron compressed about one half. Annealed 

5 hours at 650 degrees Cent 349 

Fig. 173. Stress strain diagram of malleable iron in tension for 

two rates of loading 352 

Fig. 174 Changes of strain with time at small increments of stress 353 
Fig. 175 Changes of strain with time under considerable increment 

of stress (about 70 per cent of ultimate strength) 354 

Fig. 176 Stress strain diagram of malleable iron in repeated tension 

under increasing loads 355 

Fig. 178 Behavior of malleable under cyclic cross bending at con- 
stant maximum stress 358 

Fig. 179 Maximum deflection and permanent set under cyclic cross 

bending at constant maximum stress 359 

Fig. 180 Stress deflection diagram of malleable in cross bending 

with and without previous cold work 362 

Fig. 181 Effect of torsional deformation upon subsequent tensile 

strength of malleable 363 

Fig. 182 Absorption of energy from successive impacts 364 

Fig. 183 Load deformation diagram of specimen subjected to al- 
ternate impact , 367 

Fig. 184 Magnetization and permeability curves of malleable cast 

iron .' 373 

Fig. 185 Magnetic properties of malleable cast iron 375 

Fig. 186 Variation of electrical resistance of malleable cast iron 

with temperature 377 

Fig. 187 Expansion of malleable cast iron 379 

Fig. 188 Heat transfer from machined malleable to still water for 

various temperature differences 380 

Fig. 189 Effect of temperature upon tensile properties of mal- 
leable . 382 

Fig. 190 Thermal conductivity of malleable cast iron 383 



XVIII 



American Malleable 
Cast Iron 



I 

EARLY HISTORY OF IRONMAKING 

SINCE the dawn of civilization man has continuously 
labored to use the natural resources of the world for 

his own well being. He first adapted to his needs the 
materials most easily obtained and as his knowledge and 
skill grew he sought to find or make other materials which 
would better suit his requirements. 

Copper and gold, being found in the metallic state in 
nature, were the first metals to attract his attention. More- 
over, being malleable, these metals were readily fashioned 
into the shapes desired. Far beyond even legendary his- 
tory the mound builders used copper utensils while the Incas 
and Montezumas used gold in domestic articles as well as 
in ornaments. Of the various metals found as compounds in na- 
ture, lead, silver and tin are fairly easily reduced from their 
ores ; hence prehistoric metallurgists soon added these to 
the list of available materials. Thus the age of copper was 
succeeded by the age of bronze. 

The only free iron found in nature is that of meteoric 
origin, usually existing in small fragments which easily rust 
away. However, in a few cases, notably the three large 
siderites brought from Greenland by Admiral Peary and 
now in the American Museum of Natural History in New 
York, meteoric iron has been put to industrial use. Peary's 
siderites, which are the largest ever discovered, constituted 
the only source of iron for the Esquimaux of northern 
Greenland. 

Approximately five thousand years ago, one of Pharoah's 



2 c *" AnteriCcirt m ^M(ikletfble Cast Iron 




Courtesy of American Museum of Natural History 

Fig. 1 A meteorite in the American Museum of Natural History, 
New York, brought from Greenland by Admiral Peary 

masons carelessly left one of his tools lying on the masonry 
where a new stone was being set in building the pyramids. 
Thus packed in lime, this earliest known piece of man-made 
iron was preserved for posterity. The method doubtless 
used by the Egyptian iron masters still persists in many 
semicivilized communities. 

As shown in Fig. 2 it consisted of heating rather finely 
divided ore in a charcoal fire blown by a hand or foot bel- 
lows in a shallow basin in the ground. The charcoal acted 
both as fuel and as a reducing agent, liberating metallic iron. 
The temperature being low, the iron did not combine much 
with the carbon nor did it melt freely. The pasty bloom 
which accumulated in the hearth was removed and crudely 
hammered into the desired shape. Obviously the process 
was laborious, yet it was practiced on a considerable scale. 
It is believed that the famous pillar of Delhi was made by 
welding together blooms of the kind just described. , 

Metal of this kind possessed some of the properties of 
wrought iron or unusually soft steel of the present day. 



Early History of fronmaking 



However, it doubtless was variable in quality since the 
carbon content must have fluctuated considerably due to 
the changing and uncontrolled temperature conditions. Not- 
withstanding this lack of uniformity, it was decidedly a bet- 
ter metal for tools and arms than the copper and bronze 
preceding it. 

Still before the era of written history there lived a 
primitive Carnegie whose very name has been lost. This 
early steel master, probably a native of Greece, determined 
to engage in the quantity production of iron. He substituted 
a stack or shaft for the shallow hearth then in use with the 
hope of rendering the operation continuous instead of in- 
termittent. He introduced blast from the bellows at the 
bottom, started a fire of charcoal and then began to add 
alternate layers of charcoal and ore until the shaft was full. 
Presumably he expected to dig out blooms of iron from the 
bottom of the furnace at frequent intervals and to supply 




V 



## 



m 



.r^. 





Fig. 2 A primitive furnace, 1500 B. C. The illustration was repro- 
duced from an Egyptian wall painting 



-I ntcr icon Malleable Cast Iron 



charcoal, ore and air continuously. Doubtless he was much 
surprised when on some occasion instead of iron blooms ap- 
pearing, molten metal ran from the opening in the stack. 

Such was the first production of cast iron. The better 
utilization of heat in the shaft furnace had produced a tem- 
perature high enough to more completely carburize the 
product. The decreased melting point, coupled with the 
higher temperature reached, produced a liquid metal prob- 




Fig. 3 One of the earliest blast furnaces 

\ 

ably of white or mottled fracture. Unconsciously this 
primitive artisan discovered the blast furnace. Even today 
the process of smelting iron ore is governed by the same 
general principles which obtained in the early days in Greece. 
Only the technique has been perfected. 

The earliest known blast furnace purposely to make pig iron 
is said to have operated in the Rhine provinces of Germany 
in 1311. The industry spread over the rest of Europe dur- 
ing the succeeding century. 

With the development of the crude blast furnace, one 



Early History of Irontnaking 



of which is illustrated in Fig. 3, there existed two kinds of 
iron. The one had to be forged to shape and was rather 
soft although not easily broken and the other, which could 
be cast into shape, was rather hard but too brittle and 
fragile to use. Obviously, a metal of either of these limita- 
tions was not exactly adapted to the making of swords, the 
manufacture of which constituted a most important pro- 
fession in the early days. Therefore, the most important 
metal for that age was one not soft enough to be bent 
and blunted by armor nor so brittle as to be shattered by 
a sharp blow. In the search for a material to better meet 
the requirements of the armorer some pioneer found that if 
the soft iron produced in the forge were heated in charcoal, 
the surface of the metal could be made harder in fact the 
metal could be hardened throughout if the treatment were 
continued long enough. It was learned that in this man- 
ner tools and weapons could be produced with a superior 
edge. 

For many centuries this "blister" or cementation steel 
was the only steel available. One of its principal shortcom- 
ings was its lack of uniformity across the section. How- 
ever, this was later overcome by remelting the carburized 
steel in crucibles, thus rendering it homogeneous. The 
crucible process also was modified by melting wrought iron 
mixed with sufficient charcoal or cast iron to give the desired 
properties to the metal. The amount added was determined em- 
pirically, for at that time chemical control from the viewpoint of 
carbon content was unkown. 

Thus at the beginning of the eighteenth century three 
kinds of iron were known to the world. These were wrought 
iron, soft and worked only by forging; cast iron, brittle and 
worked by casting; and crucible or cementation steel, some- 
times melted in the process of manufacture but always 
forged to shape, not brittle but hard enough to hold an 
edge and be tempered. 

Steel, however, could only be made from wrought iron, 
wrought iron only from ore, and neither could be made 
from the relatively cheap cast iron. The next forward step 
in the metallurgy of iron and in fact the first since the dark 



American Malleable Cast Iron 



ages, was the invention by Cort of the puddling furnace for 
converting molten cast iron into blooms of wrought iron by 
treatment with ore. This invention made possible the reduc- 
tion of the metal from its ore in the cheaply and efficiently 
operated blast furnace and its later conversion into mal- 
leable and ductile wrought iron. 

Steel was sitill made by using wrought iron, now ob- 
tained by puddling, as the raw material. This continued 
to be the only source of steel until the discovery of the 
bessemer process in the middle of the nineteenth century and 
the invention of the open-hearth furnace by Siemens about 
15 years later. Both of these processes, which depend for 
their success on the increased temperatures available, pro- 
duce liquid steel of nearly any desired carbon content. The 
former process uses the carbon and silicon content of the 
molten pig iron for fuel, burning these within the charge by 
a blast of air. By the removal of the carbon, the cast iron 
becomes steel which is kept liquid by the heat of combus- 
tion of the carbon and silicon. 

Siemen's was practically a modified reverberatory fur- 
nace fired by gas, the fuel and air for combustion being 
heated in regenerators by the waste heat of the escaping 
products of combustion. The oxidation *of carbon was ac- 
complished, as in the puddling furnace, by the oxygen of 
the hematite iron ore added to the slag. The essential dif- 
ference between Cort's and Siemen's invention was that the 
latter worked at temperatures sufficiently high to keep the 
resulting product molten. 

A review of the industrial world at about the close of the 
American civil war indicates that five well established types of 
iron and steel were being used. Charcoal iron was made directly 
from ore and charcoal on the same principle used in pre- 
historic "times. This material resembled wrought iron and 
was practically obsolete from a production viewpoint. 
Wrought iron was made from cast iron in the puddling fur- 
nace. It was a pasty mass and was shaped by rolling and 
hammering only. This material was soft, malleable and 
ductile. The railroad iron of which the MONITOR'S armor 



Early History of Ironmaking 



was made was of this character. A third material was 
cast iron made in the blast furnace and cast to shape in 
molds. This iron was incapable of being bent without 
breaking. The fourth material was blister or cementation 
steel made from wrought iron in unimportant amounts. 
This steel had to be forged to the shape desired. The 




Fig. A An early American blast furnace 

fifth and most important metal was steel made in liquid 
form by the crucible, bessemer or open-hearth process from 
cast iron. This had so high a melting point that it 
was incapable of casting any but large molds, hence 
it was usually cast into the latter form and rolled or 
forged to shape. When desired it could be produced of a 
composition permitting of hardening and tempering. 

A sixth product, then just coming into use is the subject of 
this volume. 

It will be observed that in none of the first five products 
are combined the properties of malleability of wrought iron 
and fusibility as found in cast iron. In other words, no ma- 
terial has been described which could be cast into intricate 



American Malleable Cast Iron 




a 



bb 



Early History of Ironniaking 9 

shapes and which would be in any degree malleable when 
complete. The problem of producing a malleable cast iron 
to fulfill these requirements had long occupied the minds of 
the iron masters. Since Cort had produced wrought iron 
by the use of ore, a modification of his process which would 
not involve the melting of the cast iron now seems to us a 
logical conclusion. In 1722 Reaumur, a French physicist, 
described a process, not necessarily original with him, for 
producing malleable cast iron by packing small castings of 
(presumably white) cast iron in pulverized hematite ore 
and heating them to bright redness for many days. This 
method evidently was suggested by the cementation process 
for making steel from wrought iron, substituting for the 
charcoal which adds carbon in that process, ore which removed 
carbon, the same reaction later discovered by Cort as applied to 
molten cast iron. 

Reaumur's discovery, or better disclosure, actually grew 
into an industry in Europe. It happened that European 
white cast irons, except in Sweden, were relatively low in man- 
ganese and high in sulphur, owing to the available fuels and ores. 
Being white, it also was low in silicon. 

Such conditions are all unfavorable to the formation of 
free carbon and consequently Reaumur's reaction was never 
complicated by the formation of temper carbon or graphite. 
In intention, at least, the annealing removed from his thin 
castings all the carbon which burned from the carbide of 
iron. 

The amount of the carbon originally present was im- 
material, in any event the resulting casting, if the anneal 
was successful, had only traces of carbon but contained all 
the other chemical elements originally present. Having 
been only moderately heated it retained its original cast 
form but approximated the chemical and physical properties 
of wrought iron. The shortcomings arose mainly from the 
fact that since carbon was removed through the surface, 
the process oould not be commercially applied to moderately 
thick sections owing to the prohibitive annealing time. 
Moreover, a casting having both thick and thin parts nat- 



American Malleable Cast Iron 



Urally would be completely decarburized in the former while 
still retaining much carbon in the center of the heavier por- 
tions. If the process were continued to completion in the 
thick sections, trouble from oxidation and scaling of the 
thinner parts would be encountered. Furthermore, it was 
difficult to be sure that the castings were annealed clear 
through, since the interior is not available for inspection. 
Any castings not annealed through would be brittle owing 
to the remaining undecarburized core. 

Hatfield in his "Cast Iron in the Light of Recent 
Research" says of this process as practiced in England : 
"Essentially, the materials used in Britain in the production 
of malleable castings, are high in sulphur, necessitating a 
somewhat lengthy anneal at a fairly high temperature with 
a view to annealing largely in decarburization. These re- 
marks apply also to the practice in France, Switzerland, 
Belgium and Germ.any." 

Production of "White Heart" Limited 

The industry thus was limited to comparatively small 
tonnages and hence to crude methods. As practiced then, 
and still practiced in England, Germany and France, the 
product is used largely for harness parts 'and small and un- 
important work. Melting is frequently done on a small 
scale either in crucibles or cupolas. The total volume of 
production is relatively insignificant in the iron production 
of Europe aUhough there are said to be 126 white heart 
malleable foundries in Great Britain. 

Reaumur's publication was productive of only the most 
meager commercial results from an American viewpoint. 
Boyden and his immediate successors attempted to anneal 
by decarburization. The metal made by the Philadelphia 
Hardware and Malleable Iron Works before the Civil war 
was "white heart", as was that of at least a number of its 
contemporaries. About 1861, however, the manufacture of 
this product in America practically ceased. A single job- 
bing manufacturer of white heart malleable continued op- 
erations until a few years ago, operating largely on European 



Early History of Ironmaking 



pig iron. At least one plow manufacturer continues to 
operate on the basis of European cupola practice and to 
turn out white heart malleable of high strength and low 
elongation. 

Many of the stock phrases regarding malleable which 
have gone the rounds for many years originated with 
"white heart" metal. For instance, the fairly widespread 
belief that malleablization takes place from the surface in, 
that the material is not annealed clear through and that 
the material cannot be used in heavy sections because of 
the unannealed center, are among the common fallacies 
handed down from Reaumur's time. Even though the 
"white heart" or Reaumur's process never has possessed any 
tonnage significance in the United States, and has been 
practically discontinued for 60 years, its faults have been 
frequently assumed to apply to the American or "black 
heart" metal by those not conversant with the facts. 

The art of making malleable castings, as that term is 
understood in America, was discovered probably uncon- 
sciously by Seth Boyden while attempting to practice 
Reaumur's method in Newark, N. J., in 1826. 

Boyden was a manufacturer rather than a scientist. 
Probably for this reason no formal announcement of a new 
discovery was made. It is presumed that in attempting to 
duplicate European practice with American pig iron, which 
is low in sulphur and high in manganese, he inadvertently 
discovered an alloy which when heated to produce deear- 
burization, graphitized instead. The product possessed all 
the properties of the best white heart metal and was more 
easily made and more uniform. Not realizing that he had 
discovered a new art, Boyden continued this work along 
the lines he found empirically most likely of success. 

Boyden left a diary covering his experiments from 
July 4, 1826, to Sept. 1, 1832. It shows that he was at- 
tempting to duplicate Reaumur's process. Under date of 
Oct. 20, 1826, he writes : "I have a piece so good it will 
not harden any more than copper". Yet from his third ex- 



12 



American Malleable Cast Iron 




Fig. 6 Statue of Seth Boyden, erected in the city park of Newark 
N. J., by citizens in memory of the man who laid the foun- 
dation for the malleable industry in the United States 



Early History of Ironmaking 13 

periment on there are allusions to graphitization. In the 
report on the third experiment he states, "Much blacker in- 
side and not half so good". Again in Experiment No. 5 he 
refers to a piece "which had been done totally well before 
rendering dark in the middle". An entry on the eighth ex- 
periment is: "Quite gray; none of the above bend or are 
good for anything". In the ninth experiment he comments : 
"Hard iron melted in coal dust from the air received no 
change but in scoria and coal dust became soft gray iron. 
A piece of Sterling (grade of pig iron) without W (prob- 
ably wrought iron) in soft gray state done (annealed) eight 
times remains gray and unmalleable". 

Boyden had been unconsciously recording the first ob- 
servation of the formation of temper carbon and its dis- 
tinction from graphite. Being still convinced that he was 
striving to produce a steely decarburized iron he refers in 
Experiment No. 11 to the fact that "the iron was tough 
when broken and was rather too dark in color". Yet in the 
next experiment he writes, "Experiment in the foundry. 
Sterling the toughest but very dark. Sprues and Sterling 
dark and good". On Sept. 10, 1826, he notes that "some 
of the pieces were tough, gray and very good". On Oct. 20 
of the same year he makes the peculiar observation that 
"the best piece I have ever seen.... was pale blue in the 
middle". 

For many years neither he nor his successors realized 
that decarburization was not essential to the process. He 
and his associates laid great stress on packing materials and 
their chemical effect upon the product. 

Inasmuch as the graphitizing reaction discovered by 
Boyden forms the metallurgical basis of the present indus- 
try, its consideration in detail will be reserved for a later 
chapter. Black heart or American malleable cast iron bears 
no metallurgical relation to the European product and its 
history begins not with Reaumur but with Seth Boyden. 



II 

DEVELOPMENT OF MALLEABLE INDUSTRY IN THE 
UNITED STATES 

SETH BOYDEN began business as an iron founder in 
1820 at 26 Orange street, Newark, N. J. Being inter- 
ested in malleable castings, he attempted to duplicate 
European practice at a time when metallurgy was prac- 
tically unknown. After six years of continuous experiment 
he succeeded in producing malleable castings, but not of the 
kind he attempted to make. 

Due presumably to the raw material available, he hit 
upon the practical operation of the graphitizing anneal and 
thus founded a new industry. Boyden operated the plant 
under his own name until 1835 when it became known as 
the Boston Malleable Cast Iron and Steel Co. The foundry 
continued under this management for two years, after which 
it was operated under various firm names by Daniel Condit, 
J. H. Barlow and others, becoming in 1907 the Barlow 
Foundry Co. This company occupied the original site until 
May, 1914, when it removed to another location and the 
birthplace of black heart malleable was razed. 

Quite naturally the early development of the industry 
centered about its discoverer and its birthplace. At one 
time Newark had eight malleable foundries, and three of 
Boyden's brothers Otis, Alexander and Frank engaged in 
the malleable founder's art. Otis operated a foundry in 
Newark from 1835 until 1837, when it was absorbed by the 
Boston Malleable Cast Iron & Steel Co. Alexander and 
Frank engaged in the business in East Boston during the 
same interval, after which Alexander was employed by 
Frederick Fuller, of the Easton (Mass.) Iron Foundry, es- 
tablished in 1752. The business later came into the hands 
of Daniel Belcher and was continued by his descendents. 

Two plants were started in Elizabethport about 1840 
and in 1841 David Meeker began to manufacture malleable 



16 



American Malleable Cast Iron 




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Development of Malleable Industry 17 

in the Hedenburgs Works. The New Jersey Malleable 
was founded at Newark in 1841. 

The information regarding the activities of the Boyden 
brothers and their contemporaries and associates is derived 
from a paper presented before the Philadelphia Foundry- 
men's association by George F. Davis. 

It would be exceedingly interesting to trace back to its 
beginnings the present, highly developed industry. Un- 
fortunately written records of the early days survive, if at 
all, only in the account books and the minutes of stock- 
holders' and directors' meetings of the older corporations. 
Such records are not open to public scrutiny and therefore 
it is difficult in sketching the early history of the industry 
to do full justice to all. 

The writer has been unable to trace in complete detail 
the early history of the industry, other . than through 
Boyden's activities. This may be due to the fact that 
these older plants did not survive or may be caused by in- 
adequate search. It seems to be of common knowledge that 
during the first half of the nineteenth century, a number of 
persons entered into the business, the plants being mainly 
located in New England and New York, at least one as far 
west as Buffalo. 

Thomas Devlin has informed the writer that when the 
Philadelphia Hardware & Malleable Iron Works, now the 
Thomas Devlin Mfg. Co., was 'founded in 1852, the com- 
pany officials knew of the existence of the Westmoreland 
(N. Y.) Malleable Works, of a plant in Worcester, Mass., 
and also of the M. Greenwood Co., of Cincinnati, which 
was founded in or possibly before 1850 and later was taken 
over by James L. Haven. 

In the early fifties, Isaac Johnson established a mal- 
leable foundry at Spuyten Duyvil. In 1872 he, together 
with J. H. Whittemore of NaugatUck and W. S. Nichols, a 
brother-in-law and representative of Walter Wood, organ- 
ized the Hoosick Malleable Iron Works at Hoosick Falls, 
New York. Some years later, Johnson also organized the 
malleable plant bearing his name in Indianapolis, which in 



18 American Malleable Cast Iron 

1883 passed into the control of the group which later be- 
came the National Malleable Castings Co. 

In the early eighties, the Walter Wood Mowing & 
Reaping Machine Co. absorbed the Hoosick Malleable Iron 
Works, enlarging the plant from time to time. The same 
organization under the style of the Walter Wood Har- 
vester Co. started the business in St. Paul which, after a 
failure during the panic of 1893 and one or two changes of 
ownership, became the Northern Malleable Iron Co. under 
Frank J. Otis. 

Much of the early development centered in New 
England, particularly in the state of Connecticut. Among 
the oldest malleable plants is what is now the Naugatuck 
works of the Eastern Malleable Iron Co. at Union City. 
Here the development work of J. H. Whittemore and B. B. 
Tuttle was done beginning in 1858. From that plant and 
that of the ^Bridgeport Malleable Iron Co. were recruited 
many of the executives who established the industry in the 
Middle West. 

The Naugatuck and Bridgeport plants, with those at 
Troy, Wilmington and New Britain became the present 
Eastern Malleable Iron Co. At a later date the village of 
Hoosick Falls, N. Y., also sent westward a group of mal- 
leable iron foundrymen. G. H. Thompson went to Colum- 
bus, John Haswell to Marion, and later to Dayton, O. 
Sidney Horsley, superintendent of the Northern Malleable Iron 
Co., and others also graduated from Hoosick Falls. 

In 1854 Duncan Forbes, a Scotchman who had previously 
resided in western New York, removed to Rockford, 111., and 
with his son Alexander Duncan Forbes, established a gray 
iron foundry. In 1859 Forbes installed an annealing oven 
and intermittently produced cupola malleable castings in 
connection with the production of gray iron stoves which 
constituted the larger part of this business. In 1864 the 
gray iron portion of the business was definitely abandoned 
in favor of malleable castings alone. 

Duncan Forbes, the first manufacturer of malleable 
castings west of Cincinnati, died in 1870. The business was 



__ Development of Malleable Industry 19 

continued and enlarged by others of his family. In 1890 
the company was incorporated as the Rockford Malleable 
Iron Works and in 1907 removed to a new location in 
Rockford, where it continues to be operated by descendants 
of the original founder. 

In 1866 Charles Newbold and Peter Loeb started a 
malleable and gray iron foundry in the east end of Day- 
ton, O., which was incorporated as the Dayton Malleable 
Iron Co. in 1869. In 1872 the business was removed to its 
present location on West Third street/ and from time to 
time the capital stock and plant equipment were increased. 

In 1916 the plant of the Ironton Malleable Iron Co. 
was purchased, and has since been operated' as the Ironton 
works of the Dayton Malleable Iron Co. In February, 1922, 
the Dayton Malleable also took over the foundry of the Timken 
Co. at Canton, Ohio. 

In August, 1868, the Cleveland Malleable Iron Co. 
was incorporated and in 1869 Alfred A. Pope became inter- 
ested in the business and immediately thereafter its presi- 
dent. In 1873 John C. Coonley, sometime of Louisville, 
and a number of men in the Cleveland company, started the 
Chicago Malleable Iron Co. The same organization, which 
in 1891 became the National Malleable Castings Co. ac- 
quired by purchase or construction, plants in Indianapolis, 
Toledo, O., and Cicero and East St. Louis, 111., besides 
steel plants whic'h are not of interest in the present con- 
nection. 

A. A. Pope and J. H. Whittemore were leading factors 
in the early growth of- the industry, the institutions over 
which they presided now being the two largest in the 
country. Many other manufacturers of malleable cast iron 
have honorable histories extending back into the sixties 
and seventies of the last century. The writer has not had 
the opportunity he could have wished to do full justice to 
the histories of some of these smaller companies. 

The industry has the distinction of numbering on its 
rolls a president of the United States, Mr. Harding having 
been one of the original stockholders of the American Mai- 



20 



American Malleable Cast Iron 







111 

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Development of Malleable Industry 21 

leable Castings Co., organized in 1905 under the leadership 
of Charles L. LaMarche. 

In this as in other industries, the growth has been 
largely in accord with the survival of the fittest. Many 
plants have been started on a moderate scale especially at 
times of great industrial activity. Some of these failed to 
survive the first period of depression encountered ; others, 
particularly in New England, continued a 'small but often 
prosperous existence, catering to a limited trade, usually in 
their immediate neighborhoods. A number of the organiza- 
tions grew in size and influence, and by sound business and 
technical methods, coupled with an aggressive policy, at- 
tained position of prominence in their fields. 

Another type of malleable foundry has sprung up in the 
history of the industry. This is the foundry which pro- 
duces a given specialty not for the open market but as a 
department of an organization manufacturing a finished 
product. Many of these foundries also have branched out 
into jobbing work when not fully employed for their own 
requirements, but are primarily operated to furnish castings 
for the product made by the parent company. In this class 
are the malleable foundries of the General Electric Co,., 
American Radiator Co., International Harvester Co. of 
America, Ebefhard Mfg. Co., Link-Belt Co., and a number 
of others." These foundries, having a definitely established 
outlet for their product and the financial and administrative 
support of a well organized industry, usually have survived 
and grown successful. However, in at least one case a found- 
ry of this character has been sold to a malleable founder 
in pereference to its continued operation by the consumer. 

The organization of a special foundry is only possible 
where the requirements of the parent company run up to 
a sufficient tonnage to make possible operations on a large 
enough scale to warrant the best operating conditions and 
supervision. The malleable industry, involving more expen- 
sive equipment and greater technical skill than the gray 
iron industry, cannot well be operated in small units on 
account of excessive overhead. Therefore, unless an in- 
dustry is large enough to operate'quite an extensive foundry, 



22 



American Malleable Cast Iron 




Development of Malleable Industry 23 

castings of better quality usually can be obtained more 
cheaply by purchase from established jobbing foundries. 

The present extent and distribution of the malleable 
industry is shown in Fig. 9. Each dot on this map repre- 
sents the approximate location of a producer of malleable 
castings. The list" is as complete as possible, having been 
compiled from the data of the American Malleable Cast- 
ings association and from information gathered for the 
government during the war. There are a number of plants 
marked as producing malleable where there is reason to 
doubt whether they have actually done so. The most recent lists 
include between 20 and 30 more plants than are shown on the 
map. In part this may be due to incomplete returns, and to a 
less degree to new foundries of very small capacity. It is un- 
likely that any important plant has been omitted. It will be 
noted that the plants are largely in the territory north of 
the Ohio and east of the Mississippi rivers, their locations 
following closely the various divisions of the Pennsylvania, 
New York Central and New York, New Haven and Hart- 
ford lines, with an additional development near Milwaukee 
and in southern Michigan. These locations were largely 
determined by the fact that they are coincident with the 
important manufacturing districts of the country, present 
good shipping facilities and are conveniently near the 
sources of fuel and pig iron. 

A more interesting compilation from the viewpoint of 
the user of malleable cast iron is the map shown in Fig. 10, 
showing the principal sellers of malleable cast iron. This 
has been prepared from the previous map by the elimination 
of foundries primarily operated as departments of larger in- 
dustries producing finished products, as for example harness 
parts, pipe fittings, etc., and of foundries whose tonnage is 
not of sufficient magnitude to be an important consideration 
from the viewpoint of the consuming interests. It will be 
seen that the distribution is almost identical, although the 
number of plants has been considerably reduced. 

Annual Production of Malleable 

The plant capacity of the United States as of 1920 is 
estimated at 1,286,300 tons annually, divided by states as 



24 



American Malleable Cast Iron 




in 



Fig. 11 Comparison of production of steel and malleable iron castings 
in the United States 

The production of steel castings is charted from the statistics compiled by the 
American Iron and Steel institute. The production of malleable iron castings is 
carefuDy estimated on the basis of the known production of plants whose output 
constitutes the majority of the annual tonnage of the country. No definite figures 
ever have been compiled showing the actual production of malleable castings and 
in the absence of such information, it is believed that the above charted values are 
as accurate as any that can be obtained under existing circumstances. 

follows: Illinois, 297,700; Ohio, 202,700; New York, 167,- 
500; Pennsylvania, 133,100; Wisconsin, 116,600; Michigan, 
108,400; Indiana, 88,300; Connecticut, 58,200; and all others, 
113,800. 

The most complete information at the writer's disposal 
indicates that there are between 176 and 204 manufacturers of 
malleable castings in the United States. In this list, however, are in- 
cluded a considerable number of manufacturers with whom 
the production of malleable castings is only incidental to 
other operations. Some of these produce malleable only 
intermittently or in small quantities, as their own need 
require, and are included here in the interest of complete- 
ness rather than: because of their importance to the job- 



Development of Malleable Industry 25 

bing trade. About 85 per cent of the tonnage of the country 
is produced by 76 manufacturers having a capacity in ex- 
cess of 5000 tons annually each. Sixty-two and one-half 
per cent is produced by 33 owners having capacities over 
10,000 tons per annum. No single manufacturer can be 
said to exercise anything approaching a monopoly, as the 
five largest interests together have only 28 per cent of the 
capacity of the country. Each of these five can produce 
30,000 tons per annum or more. The eight additional manu- 
facturers, having individual capacities from 20,000 to 30,000 
tons, account for an additional 14.2 per cent. 

Data as to the production of malleable castings in the 
United States go back only to 1913 when the American 
Malleable Castings association began the accumulation of 
statistics on this point. Fig. 11 shows the production of mal- 
leable castings by years since 1913, compared with the 
production of steel castings by years since 1904, as recorded 
by the American Iron and Steel institute. The production 
of malleable pig in 1913 was about 5 l /> times that in 1900. 
This would imply a production of only about 127,000 tons 
of malleable castings in that year. 

It will be noticed that the annual production is con- 
siderably below the annual plant capacity. The recent fig- 
ures on production of course are based on manufacturing 
operation in times of great industrial activity. Under these 
conditions, a deficit in production compared with capacity 
seems at first glance unlikely. This deficit is due to two 
causes ; first the fact that the reported capacities are doubt- 
less a little higher than the facts warrant and second that 
most of the malleable foundries had been unable to obtain 
either sufficient labor or fuel to permit the realization of 
their full production. In other words, plants apparently 
were built in excess of the available labor supply and no 
material increase in the country's maximum output of castings 
could be expected as a consequence of the erection of ad- 
ditional plants. 

In view of the lack of productivity in all lines of manu- 
facture before the 1921 depression, it is unlikely that the manpower 
of this or any other industry could be largely increased except by 



26 American Malleable Cast Iron 

increasing the productivity of the individual employe. The 
only visible remedy seems to be an increase in tonnage per 
man by the introduction of every possible mechanical aid. 
A considerable improvement may be possible by some 
means tending toward a decreased loss of time by the in- 
dividual worker, and an increase in his skill. Data based on con- 
ditions since the summer of 1921 are of course valueless on 
account of the very small production in all lines. 

The commercial development of the industry was par- 
alleled by steady progress in the technical details of malle- 
able production. As has been stated earlier in the discus- 
sion, Boyden's discovery was not the result of a logical 
metallurgical development but was the accidental outgrowth 
"of an attempt to practice a theoretically distinct art. When 
it is realized that all of this work was done at a time when 
even the chemical analysis of iron was an unusual thing and 
that Boyden and his successors blazed the way without any 
knowledge of variations in raw material and product, save 
what might be gathered by the crudest of inspection, we 
cannot but marvel at their courage and persistence in estab- 
lishing the empirical basis for the present great industry. 
Boyden, however, having a truly technical mind, left behind 
complete notes of his experiments and the results attained. 
Some of his notes already have been quoted. He recog- 
nized the presence of carbon but only in the free state, be- 
lieving white iron to contain none. He made many experi- 
ments with various packings and under different annealing 
conditions, finally concluding that red iron ore was the best 
material. He records the belief that the annealing temper- 
ature should be at least the melting point of silver. He 
considered the presence of silicon and sulphur but knew 
nothing of analysis. Under date of Jan. 23, 1829, he records 
observations as to the effect of additions of phosphorus, 
clay, lead, zinc, tin and antimony. 

Boyden's brother, Alexander, seems to have been the 
earliest mystery monger in the trade, it being related by 
Davis, on the authority XD Horace Spaulding, the last sur- 
vivor of the Easton foundry, that Alexander had a little 
pump with which he squirted something into the stack 



Development of Malleable Industry 27 

and also that he used to throw some metal into the furnace, 
creating a great volume of smoke and doubtless an equally 
great awe in the mind of the spectator. 

In 1872 Alfred E. Hammer, of the Malleable Iron Fit- 
tings Co., began to study the chemistry of black heart 
malleable at Branford, Conn. This company in 1864 had 
succeeded to the business of an earlier one, 'the Totoket 
Co. founded in 1854 for the purpose of practicing Boyden's 
method. 

In 1875 Mr. Hammer had established a chemical lab- 
oratory which was, so far as he is aware, the first in con- 
nection with the malleable iron industry. Writing of this 
laboratory he says : 

"I found that I was practically in an unknown country. 
For that reason, 'however, the work was not only interest- 
ing but positively exciting so much so that I had a mat- 
tress laid in my laboratory and with the aid of an alarm 
clock, I was able to follow the then tedious chemical oper- 
ations through the night without much loss of sleep." 

As a result of this work, he found it possible to lay 
down "a chemical ratio as between carbon and silicon, and 
manganese and sulphur," thus being the first one "to bring 
the malleable process down to a chemical proposition. " 

Among Hammer's difficulties, not the least was that at 
this period, pig iron was not made and sold by analysis. 
However, he soon applied his chemical ideas to the selection 
and mixing of irons, irrespective of brands and grades. 

The work of this pioneer metallurgist seems to have 
escaped adequate recognition since his conclusions \vere 

thought to be too valuable" trade"* secrets to 'warrant publi- 

;* 
cation. 

He certainly came to correct quantitative conclusions 
as to manganese and sulphur at a date long before the the- 
oretical explanation was even thought of. His views as to 
carbon also seem to have been far in advance of later inves- 
tigators who gained much greater general recognition. 

While not a technically trained metallurgist, A. A. 
Pope from his earliest association, with the industry strove 
by every means in his power to collect and interpret ex- 



28 



American Malleable Cast Iron 




> *-> 




Development of Malleable Industry 29 

perimental data bearing on the processes and products of 
his plants. These investigations were conducted by Em- 
merton, Benjamin and others and resulted in an accumulation 
of valuable data during the seventies and eighties. 

It is interesting to note that especially with reference 
to manganese and sulphur, Mr. Pope's conclusions were very 
similar in application to those reached at about the same 
time by Mr. Hammer. 

Among the most progressive of the malleable manufac- 
turers was the late B. J. Walker, of Erie, Pa., who pursued 
a most liberal policy with regard to the exchange of in- 
formation and did much to develop the industry. 

In 1893 McConway & Torley established in Pittsburgh 
what is frequently said to have been the first laboratory in 
the malleable industry. It was under the direction of Dr. 
Richard Moldenke, who not long thereafter severed his 
connection with that company to become associated with 
another in the Pittsburgh district. H. E. Diller, now metal- 
lurgical editor of The Foundry, was associated with Doctor 
Moldenke at this time. 

In the autumn of 1893, James Beckett, after a tour 
covering all of the malleable foundries then producing agri- 
cultural implement parts, found that none of them had es- 
tablished a chemical laboratory for works control. This 
statement does not apply necessarily to plants not engag- 
ing primarily in this specialty which were not visited by 
Mr. Beckett. 

In 1894 the Wood Mowing & Reaping Machine Co., 
Hoosick, Falls, N. Y. employed Enrique Touceda as a 
consultant and established a well equipped laboratory. 

In 1903 when the National Malleable Castings Co., 
established a works and experimental laboratory at Indian- 
apolis, the author was unable to find by diligent search of 
the literature available any adequate information of a 
definite and quantitative character regarding the chemical 
fundamentals of the process. Therefore it was decided to 
disregard precedent and to establish a sound theoretical 
basis for works control, using the information accumulated 
by Mr. Pope as a nucleus. In this connection the quantita- 



30 American Malleable Cast Iron 

tive effect of carbon, a sine qua non in the works control 
of the product, was worked out in 1904, the conclusion 
reached being apparently new to a number of the best in- 
formed malleable men with whom it was discussed at the 
time. A little later the effect, or rather lack of effect of 
manganese sulphide was also worked out. This offers the 
theoretical explanation of the practical observations of Mr. 
Hammer and Mr. Pope. 

These facts were certainly discovered independently by 
other observers, including W. R. Bean now of the Eastern 
Malleable Iron Co. In the absence of contemporary publi- 
cation it is impossible to state whether these discoveries 
preceded or followed the Indianapolis investigations. So 
far as the writer has been able to learn the Indianapolis laboratory 
was the first to successfully exercise complete works control 
on the basis of the total carbon content being the determin- 
ing factor in the quality of the product. 

During all of this time the results of none of these in- 
vestigations became publicly available and therefore it is 
difficult to accurately chronicle the scientific development 
of the art. The organizations collecting scientific and re- 
search data of value did not feel it to be sound business pol- 
icy to make public disclosures of their work. Regardless 
of whether or not this policy was fundamentally sound from 
the manufacturers' viewpoint, it certainly proved a handi- 
cap to the consumer, who remained in ignorance both of the 
theoretical principles and practical applications of the manu- 
facture of malleable castings. 

Having again severed his business connection and es- 
tablished himself as a consultant. Dr. Moldenke began to 
contribute voluminously to the technical press. Unfortu- 
nately the only sources of information open to him seem to 
have been the work in which he personally participated. 
Furthermore he was presumably handicapped by the con- 
fidential character of his relations with his clients and ap- 
parently felt constrained to speak only in somewhat gen- 
eral terms. Nevertheless he did yeoman service in striving 
for a better interchange of ideas and information, and also 
in advocating suitable technical control of the industry. 



Development of Malleable Industry 31 

His services in this direction are probably of even greater 
importance than the actual informative value of his literary 
output. The earlier literature of the subject was derived di- 
rectly or indirectly almost entirely from his publications. 

There still persisted in the engineer's handbooks and in 
the technical press a mass of ill-supported conceptions 
largely predicated on a confusion with the white heart 
process. For example, great weight was attached to the 
oxidizing action of the packing and its effect on the proper- 
ties of the product was unduly emphasized. Great dif- 
ferences also were supposed to exist between the heart and 
surface of the same casting. Similarly there was an im- 
pression that malleablizing proceeded from the surface in- 
ward and was complete at the surface before it had pro- 
gressed far at the center. A corollary to this belief was 
that very thick castings could not be annealed clear through. 

Since none of those who knew better felt called upon 
to publicly combat statements of this character, it is not 
surprising that the engineering public was left in ignorance 
and hence in distrust of the qualities of the material. More- 
over it is not surprising that in the absence of guidance by 
those better informed, some of the less intelligent and 
progressive manufacturers did not clearly understand the 
principles of the process they practiced and therefore pro- 
duced unsatisfactory castings. 

A few of the larger producers maintained adequate 
laboratory facilities to investigate and control their methods. 
The smaller manufacturers, however, had to get on as best 
they could with their own resources until the American 
Malleable Castings association undertook as one of its ac- 
tivities to carry on extensive research work for the benefit 
of its members. Prof. Enrique Touceda, of Rensselaer 
Polytechnic institute, was employed as consulting engineer 
and since 1913 has labored unceasingly to instruct the mem- 
bers of the association in sound practice and -correct funda- 
mental principles. This work was largely confidential in 
character and added little to the user's knowledge but con- 



32 



American Malleable Cast Iron 





Development of Malleable Industry 33 

tributed immensely to his satisfaction in the use of the 
product. 

At about this time, Oliver Storey published the results 
of some research work at the University of Wisconsin, deal- 
ing with the fundamentals of the graphitizing reaction. In 
the writer's opinion this was the first scientific American 
contribution to the literature of- the metallurgy of malleable 
iron. The problem has been since investigated by Archer 
and White, Merica and by the writer. A few years earlier, 
Hatfield thoroughly investigated the less important subject 
of decarburization. The theoretical aspects of graphitization 
have been studied abroad rather thoroughly. In 1881 
Forquignon published in the Annals de Chemie et de 
Physique a contribution dealing with his tests in the an- 
nealing of malleable iron and steel. Unfortunately the au- 
thor has been unable to familiarize himself with this pub- 
lication, which is said to have dealt very adequately with 
the subject. 

In 1902 Charpy and Grenet published a study of the 
graphitization of white cast iron which covers the ground 
very fully and accurately, even in the light of present 
knowledge. This publication seems to be almost if not en- 
tirely unknown in this country. Howe, in the Transactions 
of the American Institute of Mining and Metallurgical En- 
gineers in 1908, discussed critically and exhaustively the 
evidence then available bearing on graphitization. Hatfield 
in 1910 discussed the chemical physics of the precipitation 
of free carbon from iron carbon alloys in a paper before the 
Royal society. In 1911 Rueff and Goecke published a 
study of the solubility of carbon in iron and in the same 
year Ruer and Iljin discussed the stable system of iron 
carbon. Heyn summarized the contemporary knowledge of 
the iron carbon alloys at the New York congress of the 
International Society for Testing Materials in 1912. That 
these technical investigations have been of so little service 
to the American manufacturer seems a reflection upon the 



34 



American Malleable Cast Iron 




<n 

II 

I js 



o ^ 



fcfl 



Development of Malleable Industry 35 

American literature of the subject no less than on the in- 
dustry as a whole. 

Honda and Murakami in the Journal of the Iron and 
Steel Institute, of Great Britain, (1920) advanced the theory 
that graphitization does not take place directly but is a 
consequence of oxidation of carbon by CO 2 and the sub- 
sequent decomposition of CO formed with liberation of free 
carbon. In the light of his present knowledge, the author 
cannot agree with' this conclusion ; nevertheless it is a most 
interesting contribution to the theory of the subject. 

The officers of the malleable association soon realized 
that while some of the work of its consulting engineer was 
properly of a confidential character, there existed a necessity 
for the publication of authoritative information regarding 
malleable cast iron. Accordingly the association encouraged 
participation in the programs of the technical societies by its 
consulting engineer and by others qualified to speak on the 
subject. It also established an educational committee to co- 
operate with .institutions of learning and with engineering 
organizations in the dissemination of information regarding 
the product. 

Through these various activities a fund of reliable in- 
formation regarding the properties of a well made product 
is being made available to engineers. The cloud of mystery 
surrounding the manufacture of malleable castings is being 
penetrated and the conscientious manufacturer now can pro- 
duce reliable metal by availing himself of the research facil- 
ities offered by the association. 

The larger manufacturers have found it desirable to 
continue research departments under their own control for 
the investigation of their individual problems and for the 
prosecution of research in subjects beyond the scope- of the 
investigations made by the association. 

A further step forward in the industry was made when 
the American Society for Testing Materials began the de- 



36 American Malleable Cast Iron 

velopment of a specification for malleable cast iron. The 
first specification was adopted in 1904 in a perfunctory man- 
ner and apparently was dictated by a single individual. This 
specification lay dormant for 11 years but later was actively 
studied and revised until 1919 when it assumed its present 
status.* All the requirements of the specification now in 
use have been given adequate attention by a well informed 
and competent group of men and are eminently calculated 
to safeguard the interests of the consumer without being an 
undue burden upon the producer. It may be assumed that 
such future revisions of this specification will be made as 
advancing knowledge and new requirements may warrant. 

The necessities of the war also served as a great stimulus 
in this as in other industries. The limitations of labor and 
fuel and the exacting requirements of war material forced 
the attention of all manufacturers toward a closer study of 
their operations and better control of the product. 

Probably the earliest application of malleable cast iron 
was in the manufacture of buckles and harness parts. This 
was a rather natural consequence resulting from white heart 
practice where only thin cross sections could be readily de- 
carburized. Subsequently malleable castings for wagon and 
carriage parts were produced, and as the design of agricul- 
tural implements progressed malleable iron was the major 
material of construction. In fact, it almost can be said that 
this material made possible the production of agricultural 
implements at moderate prices. The use of chain belt in 
implement work and more especially the invention of the 
Ewart link started the manufacture of malleable chain belt 
as an important development in the industry. 

The railroads also became important users of mal- 
leable in the form of couplers and smaller car details. For 
many years it was possible to divide the malleable industry 
of the country roughly between agricultural implement and 
railway material plants. Indeed, this classification still sur- 

Tentative changes were proposed at the 1922 meeting. See 
Chap. XIV. 



Development of Malleable Industry 37 

vives in the malleable scrap market. Increasing train loads 
forced the abandonment of the malleable coupler for rail- 
way use about 20 years ago, although it survives on certain 
mine car and similar equipment. 

There remained, however, a considerable tonnage of 
malleable car parts. Influenced partially by unfortunate ex- 
periences with foundries selling purely on a price basis, and 
partly by the introduction of the steel underframe to over- 
come difficulties encountered with wooden details, the mas- 
ter car builders restricted the use of malleable so that the 
production of railway malleable rather rapidly decreased. 

Peculiarly enough, while malleable castings were 
viewed with disfavor by the car builders, practically all the 
standard draft gears were still made of malleable and largely 
continue to be made of that product. There is an obvious 
contradiction, for the draft gear not only is of vital impor- 
tance but is subject to more violent stresses than any other 
car part. This is explained by the fact that in general the 
manufacturers of draft rigging dealt with competent found- 
ries and secured a uniformly good product. By tests of 
their output they assured themselves against buying and 
reselling inferior materials. The agricultural implement 
trade meanwhile was largely withdrawn from the open mar- 
ket with the establishment of foundries of their own by the 
International Harvester Co. and others. 

The manufacture of malleable pipe fittings also has 
become largely the business of plants producing the finished 
product instead of the castings. These developments and 
the changed industrial conditions of the last seven or eight 
years have very largely altered the selling field for mal- 
leable castings. 

The handicap under which the railroads operated, in- 
volving curtailment of purchases, for a time reduced them 
to an almost negligible factor in the market, although jour- 
nal boxes, car wedges, derailers, draft gears, rail anchors and 
many car parts now are made of malleable cast iron. 



_38 American Malleable Cast Iron 

The automobile and allied industries entered the field 
at just about the time the railroad business began to 
wane, and are among the heaviest consumers of malleable 
castings. The applications are found in many vital de- 
tails as in rear axles, spring shackles, and hubs, as well as 
in less critical parts such as lamp and wind shield brackets 
etc. 

Another application is in some of the highest grade 
electrical starting equipment for automotive use. 

Applications in truck and tractor design of similar 
character have been made. The use of malleable castings 
for kitchen ranges has also become standardized in the 
highest grades of this product. In hot water and steam 
heating systems radiators are assembled almost exclusively 
by the use of one of three types of malleable nipples, and 
malleable pipe fittings are standard. 

During the war the industry was kept at high pitch by 
the exacting requirements of the allied governments. In 
addition to the obvious peacetime applications, such as 
railway equipment and automobile parts which were mere- 
ly increased by war conditions, several entirely new uses 
were developed. 

Among the applications in ordnance material were 
hand and rifle grenades, trench mortar shells and 75-milli- 
meter shrapnel noses. The air service required fragmen- 
tation bombs of malleable castings and the tank service 
equipment and artillery tractors developed applications 
analogous to ordinary automotive equipment but involving 
greater difficulty in manufacture. 

There is an extremely prevalent impression that the 
manufacture of woodworking and other cutting tools of mal- 
leable iron is a common commercial practice and that the 
resulting product masquerades as steel. Some material of 
this character must have been niade in times gone by, al- 
though the writer in 18 years of rather intimate acquaintance 
with the product of the largest producer and a fair familiar- 



Development of Malleable Industry 39 

ity with the output of some of the other principal manufac- 
turers has never seen any of this product. A well known con- 
sumer of malleable for other purposes states that hatchets con- 
tinue to be made from malleable iron by at least two important 
producers. 

One important manufacturer of vises is a large con- 
sumer of malleable and several concerns have made shear 
blades to which steel cutting edges are welded. This, with 
some business in the form of small hammers, and many 
wrenches, seems to be the extent of tool applications. 

Just what the future may hold in store can hardly be 
foretold. The trend toward a critical study of the proper- 
ties of all materials and comparison with the service require- 
ments of engineering details without doubt will produce 
occasional adjustment of the present conventional designs. 

The railroad business doubtless is destined to return and 
the automotive applications to increase. The opportunities 
for malleable for radiator nipples, pipe fittings, etc., where 
resistance to rust and to shocks is the determining factor, 
are great. Applications in the electromagnetic field also 
give promise of a bright future. This is equally true of 
agricultural appliances, although carriages, wagons and har- 
ness are permanently decreasing as the automotive appli- 
cations increase. The shipbuilding field also holds consid- 
erable possibilities. 

Foreign Production of Malleable 

The production of malleable iron in the Dominion of 
Canada is of fair magnitude, there being 10 plants having in 
1920 a production of about 30,000 tons in the aggregate. 

In Europe the black heart industry seems to have been 
limited for many years to a single British producer, the 
Leys Malleable Castings Co., which began the manufacture 
of black heart malleable some time between 1878 and 1880, 
and the European factories of the International Harvester 
Co. and the American Radiator Co. It is possible that rela- 
tively recently other plants have started the manufacture 
of black heart malleables in England, more especially during 



40 American Malleable Cast Iron 

the war period. It has been said that some ten or twelve 
plants now engage in that operation, but the author has so 
far been unable to obtain data as to tonnage which might 
serve as a check on the magnitude of the British industry. 
At the May 24, 1921, meeting of the British Iron Research 
association Professor Thomas Turner declared that the 
United States makes 10 times the number of malleable cast- 
ings made in Great Britain. 

Malleable Industry in Europe and Asia 

The author's most recent information regarding the mal- 
leable production of continental Europe is derived from 
conversation with Raymond Gailly, of Gailly Freres, Charle- 
ville, France. According to M. Gailly at present there is no 
production of black heart malleable in France or Belgium. 
However, many small and medium sized plants for the pro- 
duction of the European type of product are being devel- 
oped. In the larger plants, the mechanical equipment, espe- 
cially for sand handling, is in accord with the most ad- 
vanced practice. 

Lower sulphur metal is becoming available, and an 
increasing interest in the American process is developing. 
Marcel Remy of Herstal, near Liege, Belgium, has been ac- 
tive in an attempt to organize joint action by French and 
Belgian foundries toward the study of the process, having in 
mind the introduction of the American product. M. Remy 
has submitted a report on malleable iron to an association 
of" founclrymen at Liege which briefly summarizes the pres- 
ent state of the art. 

Commander Kawahigashi of the Imperial Japanese navy 
advises that there is one malleable foundry in Japan operat- 
ing on European principles and none making American 
malleable. It seems probable that this constitutes the ex- 
tent of the malleable industry of Asia. 



Ill 

METALLOGRAPHY OF MALLEABLE IRON 

A~,L,of the ferrous materials used commercially may be 
considered as alloys of iron and carbon. Their proper- 
ties are determined primarily by the character of the in- 
dividual constituents present. The possible entities or materials 
present in commercial iron and steel are as follows : 

Ferritc -Carbon free iron. 

Ccmcntite Iron carbide having the formula Fe z C. 

Austenite A solid solution of iron carbide in iron, homo- 
geneous in character and of indefinite carbon content. 

Pearlite A mechanical mixture composed of alternate 
layers of cementite and ferrite in such a proportion as to con- 
tain about 0.89 per cent carbon. 

Martcnsite, troosite, sorbitc, etc Various intermediate prod- 
ucts between austenite and pearlite. 

^Graphite Free carbon in flat crystalline plates. 
Temper carbon Free carbon in an amorphous condition. 

The common irons of commerce are all composed of various 
combinations of these ingredients, thus: 

Wrought iron is nearly pure ferrite. 

Cast and annealed steel is ferrite and pearlite. 

Tool steel (0.90 per cent carbon) when annealed is prac- 
tically pure pearlite. 

Steels which have been hardened and tempered are mar- 
tensite, troostite or sorbite with or without the presence of 
excess ferrite. 

White cast iron is pearlite and cementite, as are also the 
very high carbon tool steels (over 0.90 per cent carbon) when 
annealed. 

Gray cast iron is pearlite and graphite, usually containing 
also more or less ferrite and sometimes cementite, depending 
on the combined carbon content. 



.42 



American Malleable Cast Iron 




Fig. 15 Austenite and ledeburite in manganiferous white cast iron 



Large gray areas, austenite; speckled white and gray areas, ledeburite, the 
eutectic of cementite and austenite 
Etched with picric acid x 2000 




Fig. 16 Martensite in quenched white cast iron is shown by inter- 
lacing needle structure 
Etched with picric acid x 2000 



Metallography of Malleable Iron 



43 




Fig. 17 Troostite in steel. The dark spots are troostite 



Etched with nitric acid 



x 2000 




Fig. 18 Pearlite in incompletely annealed malleable 

Alternate bands of ferrite and cementite are shown 
Etched with picric acid x 2 000 



44 



American Malleable Cast Iron 




Fig. 19 Spheroidized pearlite 

Lamina of cementite in a matrix of ferrite are shown, the lamina being in 
part changing to globules by surface tension 
Etched with picric acid x 4000, but reduced one-half in reproduction 




Fig. 20 Graphite in gray iron 



Unetched 



Metallography of Malleable Iron 



45 




Fig. 21 Soft gray cast iron 

Black represents graphite flakes, the white areas surroundng the black are 
ferrite, the speckled areas are iron carbon phosphorus eutectic, and the gray areas 
pearlite 

Etched with picric acid x 20U 




Fig. 22 Malleable cast iron 

The black represents temper carbon nodules and the white ferrite 



x 200 



46 American Malleable Cast Iron 

Malleable cast iron is ferrite and temper carbon. 

It will be noted that the latter product differs from all the 
others in containing only free carbon and free iron. Further it 
is the only material containing temper carbon and the only 
cast material containing ferrite and no pearlite or other form 
of combined carbon. 

It owes its properties to this combination of constituents, 
and in turn it owes its metallographic composition to the peculiar 
circumstances under which it is produced. In this case, as in 
all others, the particular metallographic entities present are 
determined by the chemical composition and heat treatment of 
the alloy. 

The particular substances which are stable at different 
temperatures and concentrations of carbon were first sys- 
tematically recorded by Roberts-Austin. The Roberts- Austin 
diagram has since been modified in accord with later and more 
accurate quantitative observations, and in the light of new 
knowledge by many contributors. 

It can be shown that there are two typically distinct series 
of alloys. In one, cementite and iron are the components 
present, either free or in solution in each other, while in the 
second free carbon enters to more or less replace the carbon 
of the cementite. On the basis of X-ray spectrograms, Jeffries 
and Archer have concluded that cementite itself cannot be dis- 
solved in solid iron. Alexander has taken exception to this rea- 
soning. Without wishing to attempt an expression of opinion 
as to the merits of the controversy in a field with which he is 
but slightly familiar the author is definitely sure that two dis- 
tinct types of solid solutions exist one of or in equilibrium 
with cementite and the other of or with carbon. 

It has been clearly shown by Cesaro that molten cast iron or 
steel is a solution of cementite, Fe., in iron, Fe 2 . Volumes have 
been written to prove or to disprove the thesis that all graphite is 
derived from the decomposition of solid, or frozen cementite. 
However this may be, temper carbon is always a decomposition 
product of previously formed cementite, since the casting before 
anneal consists only of cementite and pearlite. 



Metallography of Malleable Iron 




20 % CARBON 



Fig. 23 Benedict's diagram recording the equilibrium conditions in 

terms of temperature and agraphic (non graphitic) carbon. 

It is based on Benedict's principle, somewhat modified 



In this case, at least, we may base our conclusions on the 
conditions as outlined by the Benedicks in the form of a double 
diagram. Fig. 23 sums up the principles of Benedick's views 
with sufficient accuracy for the present purpose. 

In this diagram the absissae or horizontal dimensions, rep- 
resent carbon content in per cent, the ordinates or vertical 
dimensions represent temperatures in degrees centigrade. The 
conditions of equilibrium are then represented by various lines 
and fields on the diagram. Thus above ABD the metal is a 
homogeneous liquid. A,BD marks the relation between car- 
bon content and the beginning of freezing, while AEBC marks 
the relation of carbon content and completion of freezing. In 
the area AEB and DBC the metal consists of a mixture of 
homogeneous liquid and theoretically a homogeneous solid. In 
the former area the solid has all the properties usually associat- 
ed with a solution except fluidity, hence the term 'solid solu- 



48 American Malleable Cast Iron 

tion/ The alloy of lowest freezing- point B, carbon 4.3 per cent, 
is known as the eutectic and alloys having a higher carbon con- 
tent than E, carbon just under 2 per cent, are said to be eutectif- 
erous, that is, their freezing is completed by the solidification of 
a liquid eutectic at constant temperature of 1130 degrees, Cent. 
Davenport has pointed out that the massive character of ce- 
mentite in commercial white cast iron is an evidence of super- 
cooling below the eutectic freezing point followed by the separa- 
tion of pro-eutectic cementite in addition to the cementite ot 
ledeburite. This point is of interest to the metallographer, but 
may be disregarded for the present discussion. The solidifica- 
tion of noneutectiferous alloys to the left of E is completed 
by the freezing of a solid solution of composition dependent 
on the original carbon content at temperatures marked by the 
line AE. Below the freezing point, other rearrangements 
ocur, in the solid metal. 

These transformations occur at definitely fixed temperatures 
dependent on carbon concentration. These temperatures are 
known as thermal critical points, and four important distinct 
critical points have been studied, although more are believed to 
exist. A critical point is marked by the symbol A. The four 
important ones are distinguished from one another by suffixes, 
the points being named A if A 2) A z and Acm. The numerals 
represent their relative location as to temperature, A l being the 
lowest, A 3 the highest. Acm is not strongly marked thermally, 
but represents the solubility above A^ of cementite contracted to 
cm. Critical points vary in position according as they are meas- 
ured on a rising or falling temperature. A point determined 
on a falling temperature has the letter r preceding the suffix, 
while c designates a critical point determined on a rising tem- 
perature. Thus Ac^ is the lowest critical point found on heat- 
ing from room temperature, and Ar t the same point as de- 
termined in cooling. A c point is always located as high or 
higher than the same r point due to lag phenomena. The des- 
ignations c and r originated as the initial letter of the French 
terms for heating and cooling. The A^ point represents the 
temperature below which cementite becomes insoluble. The A 2 
and A z points represent molecular changes within the iron not 



Metallography of Malleable Iron 49 

pertinent to our present discussion. These changes are called 
allotropic. Incidentally, however, the line COS marks the 
minimum solubility of cementite in the solid solution or perhaps 
better the maximum solubility of iron in the solid solution. 
Alloys below and to the left of this line are mixtures of ferrite 
and saturated solid solutions Alloys in the angle GOSE are 
homogeneous solid solutions and alloys below and to the right 
of ES are solid solutions mixed with cementite. 

For a full discussion of the iron carbon diagram, which 
is impossible in this connection, the interested' reader is referred 
to Dr. Howe's monumental work, "The Metallography of 
Steel and Cast Iron." 

The exact location of some of the lines has been ques- 
tioned on the basis of accuracy of observation. The solid lines 
of the figure indicate the equilibrium conditions in the metastable 
system Fe z C Fe. 

Freezing of White Cast Iron 

Confining attention to that area between the values carbon= 
2.00 per cent and carbon 3.00 per cent, marked at the lower 
part of the diagram as the range for commercial white cast 
iron, it is found that molten iron begins to freeze when it 
reaches the temperature corresponding to the intersection of the 
line A B with the vertical line corresponding to its carbon 
content. Thus for a carbon content of 2.50 per cent indicated 
by the line x-x on the diagram, the freezing point is at a. 
The solid material is lower in carbon than the liquid material 
remaining, thus at a temperature b the alloy x-x has a solid 
phase of the carbon content r and a liquid phase of the carbon 
content d. At the temperature e, constant for all alloys of more 
than 2 per cent total carbon, the remaining liquid or eutectic 
freezes as an alloy containing 4.3 per cent carbon. The solid 
formed just before the eutectic freezes, contains about 2 per 
cent of combined carbon. In freezing, the eutectic breaks up 
into cementite and austenite containing 2 per cent combined 
carbon identical with the solid portion' formed just before the 
freezing of the eutectic. This eutectic when frozen is known 
as ledeburite. 



50 American Malleable Cast Iron 

As the temperature decreases further, austenite is saturated 
with less than 2 per cent combined carbon, the solubility de- 
creasing with the temperature as shown by the line E S. Thus 
when the alloy x-x is at the temperature / it consists of cementite 
and a decomposition product of austenite of a carbon content ' g. 
When the temperature falls to A at the point h the solubility 
of cementite in iron becomes nil and the remaining solid solution 
then containing about 0.90 per cent carbon, is converted into 
pearlite consisting of a mixture of cementite and ferrite in 
such proportion as to give a carbon content of 0.90 per cent. 
It must be remembered that while these various transformations 
of the solid solution are going on, there exists also the cemen- 
tite formed during freezing so that below A the metal con- 
sists of cementite, pearlite (cementite + ferrite) and the socalled 
proeutectoid cementite separating along Acm. This is the actual 
course of events during the freezing of the ordinary white cast 
iron of the malleable industry. 

The system has been described as metastable, in other words, 
it is permanent as regards its components, not because actual 
final equilibrium has been attained but because further re- 
arrangement is impossible under the temperature conditions 
obtaining. If the iron be maintained sufficiently long at high 
temperature, either in cooling or by reheating, the cementite 
directly or indirectly will be converted into free carbon. 

This reaction is due to the fact that at a given tempera- 
ture carbon is less soluble when not combined with iron than 
in the form of Fe^C. The equilibrium conditions in the sLable 
system Fe C, are approximately shown by the dotted lines. 
Ruef and Bowman have located the line E'B' at 1138 degrees 
Cent. 1 degree (about eight degrees above the eutectic freez- 
ing point of the metastable alloys). The solubility of free car- 
bon, as distinguished from cementite is shown by the line 
B'E'S' although there is room for argument as to its inter- 
section with the line of nil carbon content and with A line. 
If the alloy marked xx be maintained at / a very long time, 
free carbon will precipitate and cementite dissolve until none of 
the latter remains and the system consists of free carbon and an 
alloy having an agraphitic (not free) carbon content /. If now 



Metallography of Malleable Iron 



51 



cooling be very slow the carbon can be progressively precipi- 
tated with decreasing temperature until at, or about, A lf no 
agraphitic carbon will remain. Archer maintains the solubility 
at A!, to be about 0.7 "per cent carbon and graphitization to be 
complete below that point only. 

Recent work under the writer's supervision by Austin, 
Payne and Gorton since the preceding paragraphs were written 
has demonstrated the existence of a solid solution which we 




f/? Presence OS* An Ex- 
cess 0/* 



Fig. 24. A further modification of Benedict's diagram indicating the 
results of recent research work 

have named boydenite. It bears the same relation to the 
stable system which austenite, in its generic sense, bears to 
the metastable. Carbon has been shown to have a defi- 
nite solubility as boydenite immediately above A lt confirming 
Archer's views as to the existence of a eutectoid of carbon and 
iron. The relation of the carbon concentration of that eutectoid 
as now determined to that of pearlite is contradictory to 
Archer's opinion. The solubility of carbon in boydenite has been 
accurately determined and the probable locus of the A lm line 
E'S' determined. The necessary revisions in the equilibrium 
diagram are shown in Fig. 24, which represents the best.informa- 



52 American Malleable Cast Iron 

tion now at hand on the matter. The diagram also has been modi- 
fied to take cognizance of the fact that the alloys are not binary 
but ternary containing carbon, silicon and iron. The liquidus in- 
dicated is derived from Gontermann's data interpreted in the 
light of additional experiment by Hird in the author's laboratory. 

Graphite and Temper Carbon 

Graphite and temper carbon are chemically identical and 
differ only in geometric form. Which one is formed depends 
only upon the temperature at which graphitization occurs. 
lokiche has demonstrated by radiographic means that their crys- 
talline and atomic structure is identical. If carbon forms at 
a temperature near the eutectic freezing point, hence in a nearly 
liquid medium, it can spread out into crystalline flakes of 
graphite. If it is formed in nearly solid iron at relatively 
low temperature it remains in the "amorphous" temper form. 

The terms "crystalline" and "amorphous" in this connec- 
tion are survivals of earlier concepts and in a measure 
are misleading in the light of present knowledge of what 
constitutes crystallinity. Temper carbon is actually possessed 
of crystalline structure, i. e. orientation of its atoms, but 
has not grown into a geometric crystalline form. It corres- 
ponds to graphite which has been crushed to powder and bears 
the same relation to graphite that powdered sugar does to rock 
candy. 

The function of malleable metallurgy is to produce a gra- 
phite-free casting and then graphitize this at temperatures such 
that temper carbon results. The terms "graphitize" or "graphitiza- 
tion" apply to the separation of free carbon irrespective of its geo- 
metric form. 

To this end the foundry must produce a white cast iron 
of such a composition as to be readily graphitized. The ten- 
dency to graphitization both during cooling and in annealing 
is affected greatly by the chemical composition of the product. 
Thus silicon and some of the rarer elements, notably aluminum, 
promote the formation of the stable system while sulphur, man- 
ganese, and some rarer metals retard the formation of the 
stable system. It can be seen that the properties of malleable 



Metallography of Malleable Iron 53 

iron depend largely on the total carbon present, because the 
more carbon is present the more will the ferrite matrix, of 
which the product is mainly composed, be interrupted by that 
element. Since the carbon possesses no strength, every temper 
carbon granule decreases by that much the strength of the 
product. In the early days much malleable was made high in 
carbon, owing to the advantage of a lower melting point with 
correspondingly greater fluidity. At times the carbon was 
so high, as compared with the silicon, that some graphite formed 
in freezing, making a bad matter worse, for obviously, a thin 
flake of carbon will do more damage than a spherical nodule of 
equal weight. From this practice resulted much of the "rotten" 
iron sold 10 years ago. Fig. 25 shows such a metal, in which 
' 'primary" graphite present in the original hard iron persists 
unaltered after annealing in the form of thin flakes. These are 
located between ferrite grains and cut up the structure badly. 

Use of Silicon 

Most of the malleable iron made by the better manufac- 
turers today ranges from 2.30 to 2.70 per cent carbon before 
annealing. An average for a high grade product in castings of 
fair size would probably be between 2.40 and 2.50 per cent. 
Small work, especially where the highest strength- is not needed, 
still is often made of higher carbon content, even up to 3 per 
cent, although this is not good practice from the viewpoint of 
the best physical properties. Since the size of the casting affects 
the rate of cooling it also affects the tendency to graphitize on 
freezing and hence the chemical composition required to pre- 
vent this occurrence. 

Quite generally, this tendency is held in check by controlling 
the silicon content. When little or no silicon is present, graphi- 
tization in the annealing process is retarded to a commercially 
prohibitive degree. When too much is present graphitization 
may be so much promoted as to take place during freezing. 
Most classes of work have a silicon content of from 0.60 to 
0.80 per cent. 

It is general practice and sound metallurgy to vary the 
silicon inversely with the carbon and for a given carbon, in- 



54 



American Malleable Cast Iron 




Fig. 25 Graphite crystals in malleable made from hard iron con- 
taining graphite 

Black grains represent temper carbon ; heavy black lines, graphite ; thin black 
lines, grain boundaries ; white, ferrite 
Etched with alcoholic nitric acid x 100 



versely with the cross section of the castings. The purpose of 
this practice is to select the silicon for a given carbon that the 
castings will be absolutely free from graphite. 

For rather low carbons, say between 2.10 and 2.40 per 
cent, it may be good practice to let the silicon vary at nearly 
the same rate as the carbon. For instance, 2.40 carbon and 
0.75 silicon metal has practically the same tendency to be 
graphitic in the casting or to mottle as 2.10 carbon and 1.05 
per cent silicon. In higher ranges of carbon, say from 2.40 
to 2.80 per cent the silicon may vary only three-fourths as fast 
as the carbon, .2.80 carbon and 0.45 silicon corresponding to 
2.40 and 0.75 per cent silicon. 

Extremely Low Silicon Undesirable 

The reduction of silicon to values as low as 0.45 per cent 
is not usually good foundry practice because such iron is easily 
oxidized in melting and produces pin holes and similar diffi- 
culties due to the liberation of carbon monoxide while the metal 



Metallography of Malleable Iron 55 




Fig. 26 Unannealed hard iron. The structure is always dendritic but 

varies slightly with the carbon content 
White is cementite; gray is pearlite. 
Etched with picric acid x 100 

is freezing. A casting which would prove large enough to re- 
quire the carbon 'and silicon referred to above probably could 
not be successfully made with less than 0.55 or 0.60 per cent 
silicon, thus setting a limit for maximum carbon distinct from 
consideration of strength. The maintenance of proper relation- 
ship between carbon, silicon and size of casting is usually pos- 
sible only on the basis of foundry experience and constant at- 
tention to results ; consequently these matters cannot be briefly 
and adequately dealt with in any terms of general application. 
From the consumers' viewpoint, any attempt to embody them 
in specifications would be the height of folly, because the prac- 
tice of no two plants, in matters of casting temperature, sand 
preparation, etc., would be nearly enough alike to make any one 
specification generally applicable even on a single class of work. 
The problem would be further complicated by variations in 
the size of castings. The figures previously given may be un- 
derstood, to apply to fairly heavy castings and represent nearly 
minimum values of silicon for a given carbon. Light work may 



56 



American Malleable Cast Iron 



possibly run 0.20 to 0.30 silicon higher and unusually small 
work even beyond that. On such extremely light work the 
carbon also is occasionally well above 2.80, as previously ex- 
plained, sometimes going over 3 per cent. 

It is not necessary to lower the silicon for 3 per cent carbon 




2J0 ^.00 



Fig. 27 Effect of silicon in relation to carbon on malleable. This 
graph is based on data from Thrasher's determinations 



far below that used at 2.80, partly because the tendency to 
mottle in very high carbon alloys is relatively little affected by 
the silicon. In alloys of this character the graphitization ten- 
dency is dependent mainly on the cooling rate. They should 
never be used in metal sections of any thickness since their 



Metallography of Malleable Iron 57 

freedom from graphite is dependent primarily on their rapid 
cooling. 

Sulphur and manganese have been referred to as opposing 
graphitization. These two elements unite to form manganese 
sulphide. This compound apparently has no effect on the 
formation of temper carbon. Accordingly, the absolute amounts 
of the two elements in the metal are unimportant provided they 
are in the proper proportion. It is found impracticable to fol- 
low the theoretical proportion of the two elements exactly, a 
slight excess in manganese always being necessary. 

Effect of Manganese Sulphide 

A low sulphur can be had only by very close selections of 
fuel and melting stock and is impossible of practical attainment 
except in electric furnace practice. The low manganese re- 
quired for low sulphur also presents difficulty on account of the 
manganese content of the available ores. The presence of a 
moderate amount of manganese sulphide does no harm and is 
sometimes a manufacturing advantage. The user need there- 
fore have no fear of sulphur. The only harm this element can 
do is to prevent complete graphitization in the anneal. A physi- 
cal specification for tensile properties will protect the consumer 
adequately in this point and leave the foundryman to operate 
his process to the best advantage with the fuel and stock avail- 
able. 

The value for sulphur, .06 per cent maximum, written into 
the 1904 specifications of the American Society for Testing 
Materials, and abandoned at its first revision, is particularly ill 
founded in view of the fact that very little malleable is made 
in the air furnace which does not contain about that amount 
before annealing. During the anneal there always is an in- 
crease in sulphur ranging from 0.005 to 0.03 per cent. It 
therefore is practically impossible to -produce from commercial 
raw material a product which would continuously pass this 
specification. The highest grade annealed product of com- 
merce has from 0.065 per cent to 0.10 per cent sulphur, thus 
indicating the unsoundness of the 0.06 per cent limit. 



58 



American Malleable Cast Iron 




Fig. 28 Beginning of graphitization after one half hour at 1700 

degrees Fahr. 

Black represents temper carbon ; white, cementite ; gray, martensite to sorbitic mixed 
crystals. Etched with picric acid x 100 




Fig. 29 Progress of graphitization after l l / 2 hours at 1700 degrees 

Fahr. 

Black represents temper carbon; white, cementite; gray, martensite to sorbitic mixed 

crystals. Etched with picric acid x 100 



Metallography of Malleable Iron 59 

Electric furnace metal can be produced as low as 0.01 per 
cent sulphur before annealing. The application of the desul- 
phurizing process is controlled by one producer through the 
Kranz patents. No particular advantage has been found to re- 
sult from these very low values as compared with slightly higher 
amounts and the triplex process usually is not operated to 
secure desulphurization to a point below 0.04 per cent. 

Phosphorus also has been regarded with more fear than is 
warranted. In small amounts it has no effect on the product; 
for example, iron containing 0.05 and iron with 0.15, per cent 
phosphorus would have commercially identical properties. 

When this element is increased to about 0.25 per cent it 
no longer is completely soluble in the ferrite of the finished 
product. It then has a direct effect on the properties of the 
metal. In this respect phosphorus differs from all the other 
common elements, in that its effect is not due to its action on 
the graphitizing process. 

The exact point where phosphorus begins to exert a harm- 
ful effect depends to some extent on the heat .treatment em- 
ployed. Commercial melting stock and pig iron grading are 
such that the commercial product contains from 0.15 to 0.20 
per cent of the element, usually about 0.18 or 0.19 per cent, 
which is amply safe. 

The microstructure of the unarinealed product is practi- 
cally independent of chemical composition, unless the latter be 
strikingly abnormal. The structure is always dendritic, con- 
sisting of hard white cementite and a darker ground mass of 
more or less well developed pearlite, as shown in Fig. 26. Of 
course, there are miner differences of structure as between 
different samples, lower carbon iron containing relatively less 
cementite and higher carbon more. The coarseness or fineness 
of crystalline structure is dependent upon the rate of freezing. 
In very rapidly chilled metal it may happen that a mesh struc- 
ture is substituted for the dendritic. This condition is unusual 
in castings. 



60 



American Malleable Cast Iron 




Fig. 30. Progress of graphitizatoin after 3^2 hours at 1700 degrees 

Fahr. 

Black represents temper carbon ; white, cementite ; gray, martensite to sorbitic mixed 

crystals. Etched with picric acid x 10(1 




Fig. 31 Equilibrium at 1700 degrees Fahr. after 70 hours 

Black represents temper carbon; gray and white, martensitic mixed crystals 
Etched with picric acid x 100 



Metallography of Malleable Iron 61 

Turning now to the second metallurgical step in the process, 
let us consider the changes taking place during graphitization 
in the so-called annealing of castings. 

This process has for its object, not the elimination of car- 
bon as many appear to believe, but the conversion of a 
metastable alloy containing Fe 3 C and Fe into the stable system, 
consisting only of Fe and C. This reaction involves no changes 
of the ultimate chemical composition. All of the elements re- 
main unaltered in quantity, the carbon only being converted 
from the combined to the free state, according to the reaction, 
Fe 3 C=3Fe+C. 

That a certain amount of carbon is oxidized is a mere in- 
cident in the process. The elimination of carbon is of prac- 
tical significance but is not in any sense the purpose for which 
the annealing operation is conducted. In this theoretical dis- 
cussion of the principles of malleable iron metallurgy this de- 
carburization will be disregarded and only the essential graphitiz- 
ing reaction will be considered. 

In the early part of the chapter the conversion of the 
metastable into the stable system was touched upon and the 
mechanism of the change described. The equilibrium in the lat- 
ter system is not as clearly understood as that of the former. 
This is due largely to the fact that steel and white cast iron 
furnish commercially important examples of the metastable 
system in which equilibrium frequently is attained. Consequent- 
ly there was material ready to hand and also a commercial 
necessity for the study of the system. 

Commercial Application 

Malleable cast iron furnishes the only commercial application 
of material involving the attainment of equilibrium conditions 
in the stable system. .Because the output of malleable is small 
compared with that of steel and also because the product was 
not always known and understood, even by the more progres- 
sive engineers, the theoretical aspects of the problems of mal- 
leable metallurgy received inadequate attention and the studies 
made in the laboratories of some of the universities lacked the 
advantage of contact with the commercial aspects of the problem. 



62 



.-hnerican Malleable Cast Iron 




Fig. 32 Imperfect attainment of equilibrium below AI due to too short 

a time 

Same as Fig. 31, followed by three hours at 1200 degrees Fahr. Black areas 
surrounded by white represent temper carbon ; white, ferrite ; gray, pearlite. 
Etched with picric acid x TOO 




Fig. 33 Normal malleable iron, metastable equilibrium below 

Black represents temper carbon ; white ierrite 
Etched with alcoholic nitric acid 



x 100 



Metallography of Malleable Iron 63 

Significant work leading toward the establishment of a cor- 
rect equilibrium diagram for the system Fe-C was done by 
Storey at the University of Wisconsin, Archer and White at 
Michigan and Merica at the United States bureau of stand- 
ards. Howe also gave adequate attention to the mechanism of 
graphitization in his "Metallography of Steel and Cast Iron." 

It has been pointed out a number of times in this text 
that the conversion of cementite into free carbon results purely 
from the fact that the solubility of carbon in the stable system 
is less than in the metastable. That is, solid iron will dissolve 
less free carbon than carbon in the form of iron carbide. 

When a white cast iron is maintained at a temperature 
higher than the lower critical point, Ac (1350 to 1400 degrees 
Fahr.) free carbon is slowly formed and combined carbon is re- 
duced to a corresponding degree. The rate at which this change 
takes place, while depending upon the chemical composition of the 
metal, is greater the higher the temperature. However for each 
temperature there is a definite value of combined carbon prac- 
tically independent of the total carbon content, when the re- 
action ceases completely. These values of "combined" carbon, 
measuring the solubility of carbon as distinguished from iron 
carbide in solid iron, have for their locus the line E'S f in Fig. 24. 

The word "combined" is used in the preceding sentence in 
what may be a somewhat inaccurate sense. It is intended to 
differentiate free carbon from carbon which is not in the free 
state. Whether the combined carbon corresponding to the line 
E'S' is actually combined with iron is very problematical. Quite 
possibly it is in solid solution and is not actually combined with 
iron. 

Microstructure of Malleable 

Fig. 26 shows the. structure of. a normal piece of hard iron 
as cooled in the mold. When white cast iron is raised to a 
temperature well above the Ac l point, say 1700 degrees Fahr., 
a decrease in cementite and an increase in the constituent forming 
the gray background, called "mix crystal" or solid solution, 
is observed. (See Fig. 28.) This results from the greater 
solubility of cementite at the higher temperature. 



64 



American Malleable Cast Iron 




Fig. 34 Graphite crystals produced by annealing at 2100 degrees Fahr. 

Black represents graphite; white, pearlite. Unetched x 100 




Fig. 35 Manganese sulphide in malleable cast iron. The arrows 

joint to MnS 

Etched with picric acid x 500 



Metallography of Malleable Iron 65 

As the heating at 1700 degrees is continued, temper carbon 
begins to form at the expense of cementite, as shown in Figs. 
29 and following, and finally equilibrium is attained by the 
destruction of all cementite. The structure then consists of 
temper carbon and solid solution of carbon in iron, as shown 
in Fig. 31 and is incapable of further change as long as the tem- 
perature remains unchanged. The product then is still whitish 
in fracture and very brittle. . 

If the temperature is allowed to decrease the solubility of 
carbon grows less and more temper carbon will form if the ma- 
terial is held sufficiently long at the lower temperature. How- 
ever, no ferrite will be formed at any temperature above the 
critical point. The ground mass above this point will remain a 
homogeneous .solid solution, differing only in carbon concentra- 
tion from that remaining at higher temperatures. 

If the temperature is carried down to 1300 degrees, that 
is, below Ar lf the carbon is completely insoluble, though 
equilibrium may not be reached unless the approach to this 
temperature is very slow. In case the time at 1300 degrees is 
not very long, a structure as shown in Fig. 32 will result, con- 
sisting of temper carbon surrounded by ferrite which in turn 
has a background of still incompletely decomposed mix crystal 
persisting from the higher temperature. At temperatures above 
the critical point, this ferrite separation does not occur, the 
structure strongly resembling Fig. 31, except as to detail in the 
metallic matrix. 

Still further treatment at or slightly below Ai\ will result in 
the complete graphitization of the product as shown in Fig. 32 
which represents the structure of malleable cast iron. Accord- 
ing to Archer's views as to the solubility of carbon at A 
graphitization is always completed only by treatment below A 
as outlined above. Graphitization is accomplished commercially 
by just such a heat treatment, that is, by heating first to a 
fairly high temperature for a considerable period and then cool- 
ing sufficiently slowly to a temperature below the lower critical 
point of the stable system. 

The maximum temperatures and time chosen are largely a 
matter of individual judgment. The exact location of this line 



66 



American Malleable Cast Iron 



on the equilibrium diagram unfortunately has not been the 
subject of adequate research. Much remains to be done in map- 
ping its course exactly. Our last knowledge is summarized in the 
revised diagram Fig. 24. Since there is no microscopic evidence 
of an iron carbon eutectoid it is somewhat doubtful whether A trn 
should be interpreted as ending at S' or whether there is a 
sharp inflection at 5', A tm running nearly parallel to A : to or 
toward P r . The significance of A 2 and A s in the stable system 
has so far eluded experiment, and nothing final has been ac- 



I I I 









Diagramatic Representat on 



00% 



.._cti _,.-..- 
inversion in 



>ined Carbon 






1.002 



\ 



5 



^JlE^ 



03 



Time Scale Will Depend On Chemical Composition 



Fig. 36 Chart showing conversion of combined carbon into temper 

carbon 

The graphs show the relation between the carbon remaining combined and the 
lapse of time at each of five temperatures. Note the increasing velocity and 
higher carbon content of the conclusion at high temperatures as compared with low. 



complished toward the location of 5"' as affected by variations 
in other elements than carbon. 

These points are of very great academic interest, but from 
an operating viewpoint are inconsequential. No operating 
errors will be involved in considering the line to be straight and 
joining the two points mentioned. 

Fig. 36 show r s in diagrammatic form the decrease in com- 



Metallography of Malleable Iron 67 

bined carbon according to the time of exposure to various 
temperatures. It will be noted graphs are given for each- 'of 
a number of temperatures. The horizontal or time ordinates 
have been plotted to scale ; however, the values given for this 
dimension are suggestive only, since the rate of graphitization 
and hence the time to attain equilibrium at various temperatures 
is dependent on the chemical composition with respect to other 
elements in addition to carbon. The figure is given as an ex- 
ample of what may happen rather than for quantitative inter- 
pretation. 

Speed is promoted by graphitizing the cementite at the 
highest possible temperature but to a certain extent at the ex- 
pense of quality. Temper carbon differs from graphite only in 
form. It has been pointed out that these differences of geo- 
metric form are due to the temperature of the metal in which 
the free carbon is formed. Accordingly, the two forms, temper 
and graphitic, shade over into each other by infinitesimal degrees 
and the temper carbon formed at high temperatures may grow 
so coarse and flaky as to be almost graphitic. Fig. 34 shows the 
carbon produced by graphitization at 2100 degrees Fahr. far 
above any commercially possible temperature. It will be seen 
that this carbon is purely graphitic and bears no resemblance 
to the temper form. Also the matrix of malleable iron is not a 
continuous mass but consists of an assemblage of individual 
grains as shown in Fig. 33. The character and size of this grain 
structure is influenced by changes of heat treatment, introducing 
another viewpoint for the selection of annealing temperatures. 
Moreover, high temperature may cause operating difficulties 
due to the deformation of castings, destruction of pots and 
fusing of packing material. An attempt to reduce the annealing 
period too far by a rise in temperature therefore is usually 
inadvisable. 

Commercial practice involves a maximum temperature of 
the castings of between 1500 and 1800 degrees Fahr. The time 
for maintaining the maximum temperature varies from 24 to 



American Malleable Cast Iron 



60 hours, or even longer, the longer periods properly accompany- 
ing lower temperatures. The commercial rates of cooling are 
variable, ranging from 5 to 12 degrees per hour. 

In general the best practice is opposed to the highest tem- 
peratures, the minimum time of holding and the fastest cooling 
and favors a maximum temperature not far above 1600 degrees, 
a time not less than 40 hours near that temperature, and an aver- 
age cooling rate certainly not faster than 10 degrees per hour; 
preferably less, more particularly near the critical point. 

.When properly heat treated, malleable cast iron contains no 
combined carbon except just under the surface.- It is prac- 
tically impossible to entirely eliminate these last traces of 
pearlite from the casting, but this ingredient can and should 
be reduced to the point where it is equivalent to not more than 
0.15 per cent of combined carbon as referred to the total weight 
of the casting. 

Approximately six years ago Thrasher published in 
graphic form the relation between carbon and silicon in 
while iron for constant tendencies to mottle. Based on the form 
of Thrasher's curves and known points near the middle of the 
range of composition for various classes of work, Fig. 27 has 
been prepared indicating the approximate relation between car- 
bon and silicon for various classes of work, based on the ten- 
dency to primary graphitization only. 

No attention has been given to the weakening effect of car- 
bon which sets limiting values on that element nor on pouring 
temperatures or other variables which may affect graphitization. 
The data presumably apply to ordinary air furnace practice and 
doubtless are subject to a certain amount of modification accord- 
ing to other variables. 

The more or less unavoidable oxidizing conditions in an- 
nealing remove some carbon from the surface. The extreme sur- 
face of malleable generally contains about 0.40 or 0.50 per cent 
combined carbon, while metal more than 0.1 -inch below the 



Metallography of Malleable Iron 



69 



surface is but little affected. Malleable castings sampled so as 
to include no material less than 1/8-inch below the surface will 
have nearly the ultimate composition of the original hard iron, 
except for the absence of combined and the presence of free 
carbon. If the sample is taken to include the entire cross sec- 
tion of metal the total carbon will vary with the thickness of 




Fig. 37 Changes of metallographic composition during the freezing 
and annealing of white iron 

the casting and will range from 0.40 per 'cent or even less up to 
the original carbon of the hard iron. In Fig. 37 the changes in 
carbon distribution during freezing of the hard iron and during 
its subsequent annealing are summarized in diagrammatic form. 
Time (estimated) is plotted as abscissae. At the top of the 
diagram the assumed temperature-time curve is plotted. At the 
bottom the relative weights of the various metallographic en- 
tities are recorded, the sum of course always being 100 per 
cent. Along the middle of the diagram the carbon concen- 
tration of the various homogeneous solutions (solid and liquid) 
is plotted for convenient reference. 



IV 

GENERAL MANUFACTURING AND PLANT 

TODAY all malleable foundries in the United States 
and Canada operate upon the same general principles 
although, of course, the manner of execution of the in- 
dividual operations varies with the ideas of the individual 
operator and the facilities at his disposal. 

Physically the foundries of the country differ widely 
both in size and type of buildings. The range in capacity 
of plants is probably from 50,000 tons per year down to 1000 
tons or less. If plants making malleable only as a side issue 
are included, the minimum capacity is considerably less than 
1000 tons. The plants range from antiquated structures of 
brick with low wood roofs to modern brick, concrete and 
steel buildings. 

A similar range exists in the facilities available in the 
form of mechanical equipment and, unfortunately, also in 
the personnel. It does not necessarily follow that the larg- 
est production is coupled with the best buildings, mechan- 
ism and talent although in this as in other industries, many 
things are possible for the large operator which are not a- 
vailable to the smaller. Large scale operations generally in- 
volve conditions better suited to the procurement of men 
and machinery of the highest order. 

In a previous chapter there have been outlined the prin- 
ciples upon which malleable cast iron depends for its proper- 
ties. It was there shown that the metal is the product of two 
distinct operations the making of castings of white iron 
and the malleablizing of the castings by a subsequent gra- 
phitizing or annealing process. This divides the process in- 
to two distinct stages and, generally, the plants into two 
separate parts the foundry and the annealing departments. 

Centered around each of these major departments are 
others of a contributing character such as the stockyard, 
mason's department, flask shop, patternshop, coreroom, melt- 
ing department, and chemical laboratory as foundry adjuncts 



72 



American Malleable Cast Iron 




bfi 
u> 

o 



bb 



General Manufacturing and Plant 73 

and cleaning, trimming, inspection and shipping depart- 
ments, engineering and metallographic laboratories as ad- 
juncts to annealing. Plant maintenance also requires the 
operation of a power station, machine shop, electrical de- 
partment, etc. There are additional departments not direct- 
ly of a manufacturing character, including those pertaining 
to sales, purchase, accounting, labor, costs, first aid and 
others. 

The actual shop organization by which the departments 
are subdivided between groups of executives differs widely 
in different companies. Even the largest producer, operat- 
ing- seven malleable plants, finds it wise to use a somewhat 
different organization scheme in each of its foundries. 
Small plants usually are practically "one-man" shops. One 
executive, often the proprietor, exercises supervision over 
all works activities. The scheme is simple, but incapable of 
any very great growth. 

A common method is to divide the duties among three 
major foremen or superintendents. One has charge of the 
foundry and is responsible for everything up to the delivery 
of hard castings to the trimming room; another converts 
these into the finished product; and the third is in charge 
of power plant, carpenter, machine and pattern shops, etc. 
Sometimes the last two are co ordinated under one head, 
making only a foundry and finishing department. A much 
more highly organized and efficient system is represented in 
the organization chart shown in Fig. 38, which is applicable 
only to a fairly large organization and incidentally is not 
exactly followed in any plant of which the writer has 
knowledge. 

The raw material purchased by a malleable plant con- 
sists of pig iron and scrap as melting stock ; coal, coke and 
sometimes oil, gas and electric power as fuel ; molding and 
core sand for the foundry and refractories for the furnaces. 
In addition a wide variety of general supplies is used in 
more limited quantities. 

In almost all plants the melting operation is executed 
in air furnaces which generally make two heats a day. In 



74 



American Malleable Cast Iron 



K *i-i r 




General Manufacturing and Plant 75 

some plants only one heat is made and in a very few two or 
three heats every other day and none on the intervening day. 
The latter practice is a survival of a practice in vogue 15 
or 20 years ago. Heats vary considerably in size. On a 
two-heat a-day basis, they vary in different plants from 
seven tons to 24 tons each ; on a one-heat basis, from about 
18 to 35 tons, and on a three-heat basis from five to 10 tons. 

In a few plants the cupola is employed 'for melting but 
this practice is not recommended for important work. Open- 
hearth melting has been tried by a number of producers 
and while not well adapted except to continuous operation 
and large tonnages is in successful use in a limited number 
of plants. A few small furnaces each having a capacity of 
about five tons are said to have been tried. The charge in 
most successful open-hearth installations averages from 14 
to 20 tons. 

A single producer operates electric furnaces at two 
different plants. From 10 to 12 heats and even more when 
molds are available, are 'made in 24 hours, but the metal 
is delivered to different molders so that generally a given 
molder only pours off twice per shift. In these plants heats 
range from five to seven tons and from eight to fifteen tons 
in weight depending on furnace capacity. Six and twelve 
tons are the nominal furnace capacities. 

Molding still is done by hand in many shops as it 
was in all plants 15 years ago. The patterns being small, 
many are mounted on a single gate. The pattern is pro- 
vided with a match part and the mold made in a snap flask. 
Hand operated squeezers 'have been in use for many years, 
the air-operated devices apparently not having met with 
general favor, although used in some plants. 

Recently the trend has been strongly toward patterns 
mounted on plates and vibrated by air when the cope is 
being lifted or the pattern drawn. 

In many localities no labor now is available capable 
of commercially producing molds fro'tn other than plate pat- 
terns. Consequently this form of mounting which requires 
less skill of the molder than any other, is practically forced 



76 



Malleable Cast Iron 




be 





General Manufacturing and Plant 77 

on the industry. Nearly all of the more complicated me- 
chanical devices have been tried, but so far they are not 
used extensively except for floor work, in which case various 
types of roll-over, roll-over drop and stripper plate ma- 
chines are successfully employed. 

As already stated the stna-le; molds are usually made 
in- snap flasks. Sometimes, when there is clanger of breaking 
out when pouring, the molds are strengthened with mold 
bands of strap ircn. 1 he use of jackets to prevent break- 
outs also is prevalent. The larger molds are made in box 
flasks, iron flasks being very common and desirable for use 
on machines. 

All malleable castings are made in green sand except 
for cored holes. Since only relatively unskilled help is avail- 
able, the use of three-part or other multiple-part flasks and 
loose pieces on patterns is practically impossible. Any pat- 
tern equipment which cannot be drawn straight out or rolled 
out on a flask hinge is incapable of quantity production 
under the conditions existing in most foundry centers. 

Cores generally are made of local sharp or lake sands 
using rosin, oil or some of the wood sugars as binders. As 
a rule, the work is of such character that large and complex 
cores are not required. 

A few foundries are beginning to prepare and deliver 
molding sand by mechanical means. One device for cutting 
sand on the floor is coming into fairly extended use, since 
human sand cutters are no longer available. 

Molds are commonly set on the floor by hand, although 
at least two semi-automatic devices for removing' molds have 
been tried, one of which offers prospects of successful oper- 
ation. 

No methods of molding, involving successive operations 
by a number of workers, have proved entirely successful 
thus far. Pouring is done either from hand ladles or from 
shank or "bull" ladles handled by two men, the former being 
more common. In cupola or air furnace practice molders 
catch directly from the stream as it flows from the furnace, 
the* tap hole being only infrequently closed by a clay stopper 
or iron bar. 



78 



American Malleable Cast Iron 




l 
1'a 

o ^ 



I 



O rt 
en o 



<L> c/3 
^ M 



f 

<U 

:_ 
O 

u 

Tj- 

bb 



General Manufacturing and Plant 79 

In electric furnace practice and sometimes also in open- 
hearth practice the heat is tapped into one or at most a few 
large crane ladles. Pouring is only rarely done from these 
ladles, the metal being transferred to hand ladles or shank 
ladles for pouring into the mold. 

For relatively heavy work the metal is sometimes re- 
moved from air furnaces by ladles of 200 to 300-pounds ca- 
pacity, mounted on two wheels and pushed and tilted by one 
laborer. These so-called "sulky" ladles can be used to pour 
work, but this is not often done. 

The molds are shaken out by laborers who also re- 
move large cores and break off the gates. This is easily 
possible because the white cast iron is extremely brittle ; 
indeed great care must be exercised to avoid accidental 
breakage. 

The castings are usually cleaned in tumbling barrels, 
although pickling or sand blasting is sometimes employed. 
The cleaned castings are inspected and gates and fins are 
trimmed off with light hammers. This department is re- 
ferred to as the trimming room, from this operation. 

Materials for Packing 

The castings then go to the annealing department where 
they are packed into pots, either with or without packing, 
or occasionally stacked directly into muffle furnaces. If 
stacked in pots, the pots are usually introduced into the an- 
nealing ovens by mechanically operated trucks. 

A great variety of materials is used as packing. The 
original process was thought to depend on the use of hem- 
atite ore for this purpose. Later on "squeezer" and "roll" 
scale from puddling mills came into use and great care was 
exercised to keep this rusty by the use of salamoniac solu- 
tion. At present air furnace slag is the commonest ma- 
terial, although blast furnace slag, silicaquartz, ground 
brick and many other materials can be used. A refractory 
material in granular form to support the castings is the prin- 
cipal requirement. Also the access of flame to the castings 



80 



4mcrican Malleable Cast Iron 




= 2. 

~ t/T 



General Manufacturing and Plant 



must be prevented by using a fairly fine packing and by 
keeping the pots tightly luted with clay. 

In general the pots are from 15 to 18 inches wide, 18 to 
24 inches long and 12 to 14 inches 'high, being approxi- 
mately rectangular in shape. In some cases the size of the 
work being annealed requires pots as large as 30 to 36 
inches. Large pots usually are shallow (about 6 inches 
high) on account of their great 'weight. A larger number 
of pots are used to produce the desired height of stack. A 
few plants prefer circular pots on account of their freedom 
from distortion under heat. This advantage is offset by 
their being uneconomical of floor space in the ovens. The 
pots have neither tops nor bottoms, the bottom of a stack 
being made by a special casting. The stack of bottoms and 
pots thus forms a single large container. 

Annealing 

Annealing ovens vary greatly in size and 'hold from 50 
to 350 pots arranged in stacks either three or four pots high. 
The largest type of furnace has inside floor area of 
about 625 square feet and a height of from 7 to 9 feet to 
the spring line of the arch. Such furnaces obviously hold 
enormous tonnages depending largely on how closely the 
pot space can be occupied by castings. Moderate sized 
ovens accommodate about 15 tons of castings, while the larg- 
est ovens when worked to full capacity can handle from two 
to four times as much. Some small commercial furnaces do 
not hold much over 5 tons. 

Furnaces generally are heated with coal, fired by hand 
or by stoker or burned in pulverized form. Oil, producer 
gas, and natural gas have also been used to a limited degree. 

Continuous furnaces of the tunnel kiln type, which are 
just coming into use, seem to promise great advantages, both 
economically and from the standpoint of control. 

While the heat cycle for complete graphitization de- 
pends upon certain definite scientific facts and is fixed for 
a given class of material, in practice the cycle is also de- 
pendent upon the firing conditions, the circulation of gas 
in the furnace, weight of furnace contents, etc., since these 



82 American Malleable Cast Iron 

affect the practical means for attaining the desired thermal 
cycle. 

Theoretically the cycle can be reduced to, about 100 
hours under the conditions most favorable to rapid graphi- 
tization. However, the production of the highest grade of 
metal under operating conditions always necessitates a cycle 
of at least seven days even under conditions most favorable 
to speed. Cycles of 12 to 14 days are not uncommon with 
large furnaces. 

Incidentally the consumer should be warned against a 
product made by any of the means which permit of cycles 
occupying only three or four days. Conditions can be ar- 
ranged so as to produce merchantable work in that period ; 
in fact, the writer has had practical experience with emer- 
gency annealing intended to turn out two charges a week 
from a 'given furnace, and actually doing so. However, the 
process is so tricky and the chance of inaccurate control so 
great that he is prepared to unqualifiedly condemn the prac- 
tice. Furthermore when the process works exactly right the 
conditions are such as to preclude the use of sufficiently low 
carbon iron to produce a product of the highest quality. 

The consumer should bear in mind that it is naturally 
to the manufacturer's interest to use the shortest practicable 
cycle on the score of fuel economy and decreased overhead 
for the use of furnaces. The producer therefore requires no 
outside stimulus to hurry this portion of his process and 
such a stimulus will only react against the purchaser. The 
conscientious manufacturer takes sufficient time at "a cost 
to himself, in order to produce a high grade of work and 
should not be driven from this laudable position by the ef- 
forts of "stock chasers" whose only thought is of quantity 
and time. 

When the work leaves the ovens it is separated from 
the packing, cleaned by rolling or sand blasting, subjected 
to any required machining or grinding operations, inspected 
and shipped. These operations are of a 'general character 
and are not especially characteristic of this particular in- 
dustry. Some special operations will be discussed in detail 
later. The diagram in Fig. 43 summarizes the processes by 



General Manufacturing and Plant 



83 



which the raw material is trans formed intp the finished cast- 
ings. It is evident that the process of manufacture is so 
complex that the cost *of operating a malleable foundry is 
much greater than that of a gray iron shop. The first cost of a 
malleable plant of given capacity greatly exceeds that of a gray 
iron foundry of the same size. 

The foundry buildings and operations are approximately 
identical in character and cost with tho.-e for gray iron, ex- 




Fig 43 Chart showing cycle of principal operations in a malleable 

plant 

cept that the cupola is a cheaper melting apparatus, usually 
in operation and in first cost than any of its competitors. 
When a gray iron casting passes the trimming room it is in 
a salable condition, except for some additional grinding. A 
malleab 1 e casting, however, still has to be packed, annealed, 
cleaned and straightened. In this process over half as much 
fuel is used, in many plants, as was used in the original 
{netting. The overhead also is burdensome because the in- 



84 



American Malleable Cast Iron 



vestment in annealing ovens is much greater per unit of capacity 
than the investment in melting equipment. 

The division of labor between the several departments 
may be represented with some pretense at accuracy by the 
diagram shown in Fig. 44. To a certain extent the char- 
acter of product manufactured alters the proportion shown. 
For example, a plant making small castings uses fewer la- 
borers per molder than are employed in making heavy cast- 
ings. Moreover, in a plant completely developed along me- 



/io/der& and 

Coremokers 
^6% 




Fig. 44 Chart showing division of labor in a typical foundry 



chanical lines, the ratio of unskilled .to skilled men and of 
employes to product is greatly reduced. 

It has been estimated from data gathered for use of the 
fuel administration during the war that the country's plant 
capacity for malleable castings was about 1,000,000 tons per 
annum, and the labor requirements for operation at capacity 
were 20,000 molders and coremakers and 36,000 others. This 
is in the ratio of 1.8 employes other than coremakers and 
molders to 1 of the latter group. The writer's data indicate 
a ratio of about 2.2 to 1. Both sets of figures are based on 
estimates so that an exact agreement is impossible. The 



General Manufacturing and Plant 85 

government estimate indicates further that the production of 
1000 tons of malleable requires the employment of 56 men 
for one year, or roughly that a ton of malleable represents 
a labor expenditure of about 155 hours. In the writer's 
judgment the figure is probably low as an average through- 
out the country. 

The amount of labor involved in the mere handling of 
material mechanically or manually in a foundry is seldom 
realized by those not conversant with the trade. 

Conditions vary, o>f course, very widely, depending on 
character of work, plant layout and so on, but the following 
table may be regarded as suggestive at least of the labor 
consumed in handling material for . production of one ton of 
castings : 

Table I 
MATERIAL HANDLED TO PRODUCE 1 TON OF CASTINGS 

No. of 

Tons of times Total tons 

material handled handled 

Melting stock 2.2 3 6.6 

Molten metal 2.0 3 6.0 

Sprue 1.0 3 3.0 

Slag 1 6 .6 

Castings 1.0 19 19.0 

New molding sand 35 2 .7 

Used molding sand 5.0 25.0 

Core materials .25 10 2.5 

Fuel 1.2 3 5.1 

Cinders 175 2 .35 

Annealing pots 1.5 6 9.0 

Packing 5 2.5 

Refractories 15 6 .9 

ll925 81.25 

Add 1/3 for handling supplies and equipment 27.08 



108.33 

The items in the above table are based entirely upon 
estimates. The writer knows of no attempt to actually de- 
termine the several items. Also, evidently the expense of 
handling a ton of material can have no unit cost assigned, 
for the term "handling" may mean picking up the material 
and transporting it by a crane; picking it up to inspect, 
piece by piece, or the laborious operation of firing a ton of 



86 



American Malleable Cast Iron 




bfl 




General Manufacturing and Plant 87 

coal in an air furnace, or wheeling a ton of sand a consid- 
erable distance by hand. The table is here presented pri- 
marily .to show the importance of reducing the number of 
handlings each material undergoes and facilitating each by 
every available means. 

The 'history of labor in the malleable industry has been 
that of labor in all similar work. In the early days the 
workers were practically native Americans, supplemented by 
thoroughly Americanized English, Irish, Germans and Scan- 
dinavians. Later the two latter groups increased consider- 
ably, and still later toward the end of the last century the 
influx of Balkan immigration began. The native American 
and the original foreign 'groups meanwhile drifted almost 
entirely out of the labor and molding groups, though a few 
remain principally in the coremakers' trade. Most of these 
men and their sons headed toward the machinists, carpen- 
ters and patternmakers' trades, or toward other employment 
of similar character but requiring less skill. 

Type of Workmen Available 

Meanwhile the Hungarians, Bohemians, Poles and Aus- 
trian-Slavs began as laborers and gradually worked upward 
through the various grades of skill, being supplanted in the 
lower grades by Italians and later by Bulgarians, Greeks and 
Russians, and still later by Turks and Armenians. In some 
few plants the negro long has been employed in all but the 
highest skilled trade 1 - and the northward migration of the 
southern negro farm laborer is rapidly enlarging this condi- 
tion. Postwar developments meanwhile are making for the 
return of many former subjects of Austro-Hungary, Bulgaria 
and Russia to their native lands. He were a rash prophet 
who would attempt to discuss the net effect on the Amer- 
ican labor market of this emigration, the European tendency 
toward immigration to America, the discontent of those who 
returned to Europe, the industrial stagnation of Austria and 
Russia, all in the light of the American immigration laws 
and shipping facilities. Natural clannishness of foreign races 
has produced a segregation of nationalties in different parts 



88 American Malleable Cast Iron 

of the country. The lines of course are not rigidly drawn 
but the Scandinavian still persists in (the northwest and 
to some degree in the St. Louis district. In the terri- 
tory extending from St. Louis to Terre Haute the Armenian 
is relatively prevalent ; the Russian and the Pole have set- 
tled in the Chicago district, as also the older class of Bo- 
hemians. The region around Indianapolis is manned by 
Greek, Bulgarian and Austrian-Slav foundry workers, while 
in northern Ohio Poles, Bohemians and Italians dominate. 
The latter element is very prevalent through the Pittsburgh 
district and through the Shenango and Mahoning valleys. 
New England and New York, being gateways to the in- 
terior, probably have a more mixed population than the Mid- 
dle West. 

Foundries of all kinds have been confronted with these 
conditions : First, a growing disinclination on the part of 
all labor to do foundry work; second, a trend toward less 
and less skilled and intelligent help; third, a more and more 
turbulent character of help from which the required force 
must be recruited. The trend toward negro labor repre- 
sents a turn in the tide at least in the latter respect. 

The industry is confronted with growing labor problems 
the solution) of which requires the best efforts of its ablest 
executives. These efforts will have to continue for a long 
time to come in order that the decreasing productivity of 
labor may be prevented from being reflected in the product 
in the form of prohibitive rates. 

The solution is in the utilization of mechanical aids to 
the utmost and in an enlightened labor policy. 

Metallurgy of Malleable Is Complicated 

Furthermore the malleable process is metallurgically more 
complicated' than that of either gray iron or steel foundry 
practice, and the chemical range consistent with good results 
is smaller than in the former. 

The most successful means of overcoming these handi- 
caps in manufacturing cost is to operate upon a sufficiently 
large scale and on more or less specialized products in order 



General Manufacturing and Plant 89 

to take advantage of those manufacturing economies asso- 
ciated with such production methods. 

By inference the malleable industry is not well fitted 
for the manufacture of so-called short orders, that is, orders 
involving only a few pieces from a given pattern and small 
tonnages for a given consumer. It attains its greatest suc- 
cess when operating on orders of sufficient magnitude for each 
type of casting to warrant investment in the best possible 
pattern equipment and close study of each step in the 
manufacturing. 



V 

MELTING STOCK 

THE raw materials of the malleable industry may be 
classified as melting stock, fuel and refractories. The 
remaining materials are not peculiar to the malleable 
industry and therefore are not important in the present dis- 
cussion. 

Regardless of what melting process is employed in 
making malleable, the melting stock is selected from the 
same general classes of material. Sprue, which includes 
the feeders, runners and defective castings produced inci- 
dentally to the plant operation, is seldom if ever sold and 
never is bought by a malleable foundry. Being a product 
of the foundry-man's own plant, its composition and condi- 
tion are known to him and the material requires no "further 
description. 

Malleable scrap is a material derived in part from the 
work condemned at the plant after annealing. Also it is 
an article of commerce in the form of scrap material con- 
sisting of worn out malleable parts. The* scrap yard of a 
malleable foundry is shown in Fig. 46. Scrap has been some- 
what roughly divided into "railroad malleable" and "agri- 
cultural malleable." The distinction is actually one based 
on size of castings rather than on the former use. "Auto- 
mobile malleable" is regarded by some users as a legiti- 
mate subdivision but really does not differ materially from 
the railway malleable scrap from a metallurgical standpoint. 
Pipe fittings, often classed separately, could equally well be 
included with agricultural malleable scrap. 

The composition of purchased malleable of course is 
entirely conjectural and there is therefore a limit beyond 
which its use introduces serious uncertainties as to compo- 
sition of charge. It is safe to assume that railway and auto- 
mobile malleable, before annealing had a carbon content 



92 



American Malleable Cast Iron 




i 



Melting Stock 93 



averaging about 2.50 per cent. No two pieces are alike in 
carbon, depending both on the original carbon and the de- 
gree of decarburization in the anneal, but the remaining car- 
bon in work of these heavier classes is likely to be around 
2.00 per cent or a little under. The silicon is likely to av- 
erage around 0.70 per cent and in malleable scrap consist- 
ing of castings worn out in service the sulphur is from 0.06 
to 0.10, the manganese 0.25 to 0.35 and the phosphorus from 
0.16 to 0.20 per cent. In the case of agricultural and other 
light work, the initial carbon may have been considerably 
higher, but in view of the lightness of cross section this ele- 
ment may have been much reduced, possibly to 1 per cent 
and under. The silicon generally is somewhat higher than 
in the heavier materials, usually averaging about 85 per 
cent. The other elements are about as in railway malleable. 

Malleable scrap is open to the objection that when used 
as a considerable percentage of the mix in air furnace or 
open-hearth practice, serious errors may be introduced in the 
chemical composition of the charge. This condition is ag- 
gravated if the malleable scrap includes gray iron scrap rich 
in carbon, silicon and phosphorus. It is a most reprehen- 
sible practice of a number of junk dealers either to purposely 
mix or to not properly separate the two materials, thus 
practically destroying the value of the malleable scrap to 
the malleable founder. This separation can be readily made 
only 'at the point of origin as the user has no commercially 
effective method of inspection. Equally harmful in the op- 
posite direction is the admixture 'of steel. 

Another source of -trouble is the introduction of un- 
known amounts of rust into the charge when melting scrap 
that has been exposed to weather. Some scrap may con- 
tain 5 per cent or more of rust which of course is a dead loss 
in melting. It also forms a highly oxidizing slag which in 
turn strongly acts on the silicon and carbon causing unpre- 
dictable changes of composition in melting. The -effects of 
this evil can be minimized by the use of clean scrap, which 
unfortunately cannot be purchased and by the purchase of 



94 American Malleable Cast Iron 



scrap of such form that it presents little surface to rusting. 

For this reason and because of the high labor cost of 
handling small scrap, agricultural material is not a satis- 
factory melting stock in air furnace or open-hearth mal- 
leable practice. Heavy malleable scrap stored out doors 
but not extremely heavily rusted usually behaves as though 
it contained about 1.75 per cent carbon and 0.47 per cent 
silicon. The presence of adulterations, except of high phos- 
phorus material, is of less consequence in electric furnace 
melting than with air furnaces or open 'hearths. Malleable 
scrap is used not because it is a means of cheapening the 
metal but for the definite purpose of regulating the carbon 
content of the mix. Successful air furnace practice requires 
a c'harge averaging around 3 per cent in carbon, hence some 
low carbon stock must be used to mix with pig iron which 
is always of much 'higher percentage of carbon content. 

Sprue is available in a quantity dependent on the found- 
ry practice but not usually sufficient to bring down the car- 
bon as far as necessary. Hence recourse is had to mal- 
leable or steel scrap. The use of scrap for the purpose of 
making up different 'amounts of sprue has been practiced for 
more than 30 years. The Chicago Malleable Iron Works 
has purchased scrap for air furnace charges on a commer- 
cial scale since 1885 and in 1888 the practice was well es- 
tablis'hed. Possibly others adopted it still earlier. 

Steel scrap is an article of commerce. What has been 
said of -malleable regarding freedom from rust and from ad- 
mixture of other forms of scrap applies equally well to steel. 
In addition there is a certain danger from the possible pres- 
ence of alloy steels which may introduce entirely unexpected 
elements. A case in point is the high manganese steel used 
in frogs, switch points and cross overs and containing up to 
about 13 per cent manganese. 

The carbon content of all steels is relatively low, rang- 
ing from around 0.90 to 1.00 per cent in some spring steels 
down to 0.25 or 0.30 per cent in castings. The silicon is 
always low and the manganese averages around 0.50 or 0.60 



Melting Stock 95 



per cent. The sulphur and phosphorus values are always 
lower than in any other ingredient in the charge. Consid- 
ering the fact that the material is always somewhat rusty it 
may be classed as pure iron in calculating a mix. 

Heavy steel scrap is preferable to the lighter material 
as is the case with malleable scrap. Thin sheet, small clip- 
pings, rods, pipe and light structural material are particu- 
larly objectionable when rusty or burned. 

Steel, as in the case of malleable scrap, is used to reduce 
the carbon content of the mix. Being lower in carbon a 
less percentage suffices for a given purpose ; therefore there 
is less danger of introducing large errors of calculation in , 
computing the mix or of large amounts of rust to compli- 
cate the reactions. 

Steel is rarely used in making cupola or electric furnace 
malleable. Its general use was adopted more recently than 
that of malleable scrap, but the old records of the Indian- 
apolis plant of the National Malleable Castings Co. show that for 
an extensive period, beginning in August, 1887, steel was 
regularly vised in the mix, and that the practice continued 
as circumstances warranted. The author has no facts to in- 
dicate whether this practice was original with the late 
James Goodlet, then in charge thei;e, or copied from some 
other plant. 

Wrought iron, which chemically is merely an extremely 
low carbon steel, was used at the inception of the industry, 
Boyden referring to it in his notes. At a later date it was 
regarded as harmful arid at present it is not available in 
sufficient quantity to possess interest. 

Pig iron is the raw material which makes up the bulk 
of the tonnage from which malleable cast iron is made. In 
the days of the fathers of the industry charcoal iron was 
generally if not universally used. Then, as now, it was 
made from relatively low phosphorus ores. In the early 
days, before the Civil war, the references are mostly to 
irons smelted in New Jersey arid Connecticut from eastern 
ores using charcoal from local forests. Bovden used such 



96 



American Malleable Cast Iron 




Melting Stock 97 



irons. Alfred Hammer used New Jersey coke arid anthra- 
cite pig as early as 1878. In about 1885 there was 'a no- 
ticeable trend toward the use of coke-melted pig iron, first, 
as far as the author can judge, in the case of very soft pig 
iron. This was high in silicon, and was unusual in furnaces 
operating as cold as did the usual cold blast charcoal fur- 
naces of the period. 

The impression is quite general among the older found- 
rymen that, apart from differences of composition, there 
are differences in properties as between the products of 
different furnaces. Many also believe that it is preferable 
to use iron from several producers in each heat. It is not 
clear to the author upon what metallurgical considerations 
such differences could be based. Undoubtedly before the 
days of analyzed pig iron, these beliefs were based on sound 
reason; at present they would seem to be little more than 
prejudice as applying to malleable practice. 

A similar situation is encountered in a somewhat gen- 
eral feeling that the use of malleable scrap is in some way 
connected with the substitution of coke for charcoal pig. 
It has been only relatively recently that interest in the 
control of the product by limiting the total carbon content 
became at all general. Dr. Moldenke in his book, "The 
Production of Malleable Castings" (1911), recommends for 
instance that the carbon be not below 2.75 per cent and 
may range up to 3 per cent. Presumably this represents 
the best general understanding of the time. While since 1906 
certain manufacturers realized the relation between carbon 
and strength and acted on this knowledge, it is not sur- 
prising that in the days when the substitution of coke for 
charcoal iron began the mixes used never were based on 
considerations of carbon content. 

With low silicon charcoal iron available it was easy to 
secure silicons low enough to produce a white fracture by 
the use of pig and sprue alone. Hot blast coke irons always 
contained enough silicon so that some material other than 
the available amount of sprue was required to reduce the 



98 



American Malleable Cast Iron 




Tf 

bb 



Melting Stock . 99 



silicon content sufficiently to avoid "mottled" castings. The 
effect of this change of practice on carbon content was totally 
disregarded except by a very few observers. 

The general observation that charcoal iron malleable 
could and should be made lower in silicon than malleable 
for the same purpose made from coke iron probably was 
true. However, it originated merely from the reduction in 
carbon which unconsciously accompanied the changed prac- 
tice and not from the method of making the pig. 

Where malleable was made from charcoal .and coke 
iron of the same silicon content the former was somewhat the 
stronger, due to its somewhat lower carbon content, which 
in turn was due to lower furnace temperature. 

In view of such former experiences great caution should 
be used in regarding as cause and effect phenomena without 
apparent logical connection. 

The transition from charcoal to coke iron has extended 
over many years and is not yet complete. In the early 
ninety's coke iron was used very sparingly, but 10 years 
later the coke iron was far in the ascendant. At present 
comparatively few manufacturers continue the use of char- 
coal pig and they employ it only in limited quantity. 

To the writer it has seemed that this retention of char- 
coal iron results either from sentiment pure and simple or 
from a superstitious belief that for some unexplained rea- 
son a modicum of charcoal pig imparts a mysterious virtue 
of unknown character to the resulting product. Being 
smelted at a lower temperature, charcoal iron differs from 
coke iron in being generally lower in carbon. On account 
of the low sulphur fuel, it is always lower in sulphur. Also 
the range of silicon values commonly available run lower in 
charcoal than in coke iron. Again, this is the result of the 
furnace temperature. 

The lowest silicon charcoal pig irons commercially 
made contain less silicon than the lowest silicon grades of 
coke iron. Moreover, high silicon coke iron is more com- 
monly obtainable than charcoal iron with the same con- 



100 



American Malleable Cast Iron 




be 
c 
'-5. 

rt 
O 



Melting' S-otk : 101 



tent, in spite of the fact that the "Scotch" grades of charcoal 
pig have a high silicon content. 

The writer has never been able to see any theoretical 
reason why charcoal iron should make a better product than 
coke iron, given a correct final composition. The late J. B. 
Johnson Jr., who dealt at length with the subject from the 
blast furnace viewpoint, ascribed the differences to the in- 
direct effect of oxygen. For the best available opinions in 
this subject, the interested reader is referred to the pub- 
lished reports on Johnson's pioneer w r ork on this subject in 
the Transactions of the American Institute of Mining and 
Metallurgical Engineers. In view of the radical alterations 
made in the raw material during the malleable process it is 
difficult to see how any differences, such as the form of 
crystallization of graphite in the pig iron, could survive the 
chemical and physical changes involved. The trade as a 
whole seems to look upon the matter in this light and from 
a tonnage viewpoint, charcoal iron is of little importance in the 
malleable industry. 

The production of malleable cast iron requires the use 
of relatively low phosphorus ores, those of the Lake Superior 
region being the most available for the purpose. Conse- 
quently, many of the blast furnaces producing malleable pig 
are situated along the lake ports. The proximity to the 
Pennsylvania coal fields producing coking coals, has formed 
another area extending from Pittsburgh down the Ohio river 
and up the Mahoning and Shenango valleys. The charcoal 
furnaces are located near the ore fields in heavily wooded 
districts. The ore fields of Minnesota, Wisconsin and north- 
ern Michigan are shown in the form of a shaded area in 
Fig. 47. Immediately adjacent to this section are the prin- 
cipal charcoal furnace plants, shown on the map by open 
circles. The coke furnace plants are shown as solid circles. 
Most blast furnaces do not make pig iron for one purpose 
only, but the map is intended to include all important pro- 
ducers of this class of metal in considerable quantities. An 
open pit mine on the Mesabi range "is shown in Fig. 48. 



102 



Matictiblc Cast Iron 




Melting Stock 103 



The ores from which malleable pig iron is made 'have ap- 
proximately the following composition : 

Per cent 

Fe 51.5, present as Fe 3 O 3 . . 75.57 

P .086, present as P 2 O 5 19 

Mn. .40 to .70, present as MnO ' 77* 

Si0 2 9.50 

A1 2 3 2.75 

CaO 70 

MgO bO 

H 2 O, CO 2 and undetermined 10.02 

^Average. 

Malleable pig iron is sold with ti guaranteed maximum 
of 0.05 per cent in sulphur, usually of either 0!19 or 0.20 
per cent in phosphorus and is furnished with from about 
1.00 to 2.00 per cent silicon, although 'higher values are 
sometimes required. The manganese varies from about 0.50 
to .about 0.90 per cent, the lower and higher values being 
encountered frequently. The average carbon content for the 
country is now and lias been for at least 15 years close to 
4.10 per cent, individual lots running normally from 3.85 to 
4.40 per cent, 'i he carbon content practically is fixed by the 
blast furnace temperature. 

Pig iron may be either sand, chill or machine cast. The 
former 1 carries with it a certain amount of sand fused into 
the surface. The chill and machine cast irons are free from 
this foreign matter, which fact presents a certain advantage 
both because nothing but iron is paid for and because less 
dirt is carried into the furnaces. The two latter classes, 
being rapidly cooled, contain more combined and less free 
carbon than the former, other things being equal. The 
melting point and, presumably, the latent heat of fusion are 
thereby decreased. It is claimed that a material fuel econ- 
omy results. On all accounts the use of machine cast iron 
can present no disadvantages to compensate for the advan- 
tages outlined above and its greater uniformity of size and 
form. 

Recently there his been a decided tendency toward 
changes in chemical composition of commercial pig iron. 
Up to 1914 the sulphur content, while guaranteed as 0.05, 
was nearly invariably under 0.03 in the Ohio and Illinois 



104 



American Malleable Cast Iron 




Melting Stock 105 



irons. Since then fuel conditions have so far deteriorated 
the quality of coke available that at present sulphur is usually 
only a little under 0.05 per cent and occasionally exceeds 
that figure. Ten or 15 years ago iron often was sold with 
a maximum phosphorus of 0.16 per cent, no extra price be- 
ing charged as compared with a 0.19 or 0.20 per cent maxi- 
mum specification. The gradual increase in the ratio of 
phosphorus to iron in the product of the Mesabi ore fields 
has, however, forced an increase to the latter figures as a 
phosphorus maximum. 

For about five or six years there has been a decided 
trend toward lower carbon malleable, brought about by the 
demand for increased quality of product. This results in 
lower percentages of pig iron in the mixes than formerly 
and therefore requires increasingly a higher silicon content 
to maintain the former silicon values in the product and in 
some cases raise them -slightly. Accordingly the metal con- 
taining under 1.25 per cent silicon is now almost useless 
and most -plants require some pig iron up to 2 per cent and 
possibly over in silicon. The average silicon content in all 
the pig iron consumed in the malleable industry is doubtless 
between 1.60 and 1.70 per cent. 

There seems to be increasing difficulty in getting any 
low manganese pig. However, this stringency has been 
somewhat counteracted by the decreased amount of pig re- 
quired and the increased sulphur content. Coke pig iron 
under 1 per cent in silicon and usually high in sulphur, is 
generally the product of an abnormal furnace condition, re- 
sulting in cold working and is not of a composition suitable 
to modern requirements. 

High, silicon pig, or blast furnace ferrosilicon is a metal 
usually running about 10 per cent in silicon. Its principal 
source is Jackson, O. The phosphorus, sulphur and carbon 
are kept low. The metal is used as a source of silicon when 
suitable pig is not available. In the electric furnace process, 
it may furnish most of the silicon of the cupola charge. 

Ferromanganese is a blast furnace product made from 
manganese ores. It usually contains from 70 to 85 man- 
ganese and nearly 6 per cent carbon. Silicon, sulphur and 



106 



American Malleable Cast Iron 




be 



Melting Stock 107 



phosphorus are low, iron being the principal element, other 
than manganese and carbon. Ferromanganese is used gen- 
erally in -the form of an addition to the molten metal to 
supply a deficiency in manganese. 

Electric furnace ferrosilicon contains nominally 15, 50, 
75 and 95 per cent silicon. The 50 per cent alloy, actually 
running from 48 to 54 per cent silicon, is most commonly 
used. In addition to silicon and iron the metal contains 
phosphorus, sulphur, aluminum and calcium. These elements 
are not usually present in important amounts. 

Ferrosilicon, being readily oxidized, is not suitable for 
cupola use. When charged into an air furnace with the 
melting stock it must be protected from contact with fur- 
nace gases as far as possible. It is generally used as addi- 
tions to the molten heat. 



VI 

FUEL AND REFRACTORIES 

THUS far we have dealt with the raw material actually 
entering the product. There remain two other classes 
of raw materials which, although they form no part of 
the finished product, are used in such quantities and so affect 
the shop operation as to be of decided industrial importance. 
The first of these groups is fuel. 

The fuels used in the malleable industry may be classi- 
fied as melting fuel, annealing fuel and power plant fuel. 
The latter, although it may be used in large quantites, as 
in electric furnace plants, should be considered from the 
viewpoint of power plant practice rather than from a 
metallurgical angle. Melting fuels not only furnish heat but 
also very distinctly affect the composition of the resulting 
product. On the other hand, annealing fuels need be consid- 
ered only from the standpoint of combustion. 

The original source of almost all the heat used in melting 
and annealing malleable is coal, although it may be convert- 
ed before use into coke, illuminating gas, water gas, or 
producers gas. Oil and natural gas are also industrially im- 
portant in some localities and for some purposes. 

Bituminous coal is very widely distributed throughout 
the country, as indicated in Fig. 53. Anthracite and lignite 
are not important metallurgical fuels and are therefore omit- 
ted from the map. Anthracite was formerly used as a cupola 
fuel and at an early date, possibly 1838 was used for anneal- 
ing by Belcher. It is still used in at least one plant for 
this purpose. 

Coal from practically any of the bituminous fields shown 
may be used for annealing, the choice generally being based 
on geographic and commercial considerations rather than 
on the properties of the fuel from any given field. Mine run 
fuel is generally used in annealing for hand firing. The crite- 
rion of quality is the absence of ash and water, these fac- 



110 



American Malleable Cast Iron 




bo 
_c 

5 

o 

02 

C/3 

ex 

n5 
I 



Fuel and Refractories 111 

tors representing increased cost and operating trouble and 
not metallurgical suitability. -A low ash fuel is sometimes 
preferred for use with pulverized fuel annealing equipment 
in order to avoid trouble from the ash settling in the fur- 
naces and flues. The requirements of a crushing plant prac- 
tically necessitate a fuel either quite dry as received or 
dried artificially before crushing. 

- Since lump coal is of no advantage, pulverized fuel 
plants buy the smaller commercial sizes of fuels. However, 
the selection of fuel for crushing in annealing practice is not 
well standardized. The author knows of two large and ably 
managed plants within a few miles of each other, both an- 
nealing with pulverized fuel. One buys a high ash local coal 
and removes about 10 to 12 per cent of water by drying be- 
fore crushing, while the other obtains coal in the eastern 
fields hundred of miles distant which runs under 2 per cent 
in water. and around 3 to 4 per cent in ash. The subject 
of coal for 'annealing is therefore easily dismissed with the 
statement that practically any local fuel can be employed, 
economical conditions alone governing the selection. 

In the case of the melting coals conditions are quite 
different. Here, in addition to the purely economic prob- 
lems, there enter many other considerations which narrow 
down the choice. Coal burned in the air furnace is expected 
to furnish heat units as economically as may be practicable, 
and must have certain other definite characteristics. It must 
burn with a long luminous flame jof sufficient volume to en- 
tirely fill the air furnace. It must be so low in sulp'hur as not 
to prohibitively raise the content of- that element in the met- 
al. 

Its character must be such that none of the constituents 
will melt and run to a tarry mass at the temperature of the 
fire. Its ash must be fairly low in amount and of such char- 
acter as not to fuse together into clinker's at fire ibox tem- 
peratures. Its moisture content must -be reasonably low in 
order to maintain good flame conditions. 

These characteristics are found in coal from a very limit- 
ed geographical area which is shown in black in Fig. 53. 



112 



American Malleable Cast Iron 




bo 



'Fuel and Refractories 113 

In the writer's experience the fuel varies even within this 
district, 'being in general better in the southern portion of the 
area. 

No entirely satisfactory method of judging the quantity 
of a melting coal, except by actual test is available. This 
arises, in part, from the fact that the behavior of the fuel is 
dependent on the actual combustion conditions encountered 
which differ with different furnaces. The composition of a 
few good melting fuels is shown in Table II. 

Table II 

ANALYSES OF MELTING GOALS 



Origin 
Sulphur 
Moisture 


Pennsylvania 
0.70 
062 


West 
Virginia 
0.45 
0.76 


West 
Virginia 

1.55 
1.34 


Kentucky 
0.45 
1.10 


Vol. Comb. . 


35.63 


37.15 


41.70 


33.95 


Fixed carbon . . . 
Ash 


, . . . 58.32 
5.43 


55.64 
6.45 


52.40 
4.56 


60.68 
4.27 



B.t.u. per pound.... 13,902 13,434 14,058 14,276 

There is a general preference for coal under 1 per cent 
sulphur, although the sulphur which the melt takes up de- 
pends not only on the sulphur content of the fuel but also 
on the form in which it is present. Some fuels, moderately high 
in sulphur, produce metal lower in sulphur than other fuels, 
much lower in that element. Many coals exist, even some in the 
Illinois, Indiana and central Kentucky fields which based on 
composition should work admirably. The expectation, however, 
is not borne out in practice. 

What makes a long flame coal has never been definitely 
determined. The flaming coals are in general the coals best 
adapted to making illuminating gas. The flaming quality 
is associated with the distillation products of the fuel when 
heated in the fire box. The running of the coal is a phenome- 
non of the same character. The low moisture seems to be 
a necessary characteristic. Goals of this character artificial- 
ly wetted behave differently from the naturally wetter In- 
diana-Illinois fuels. 

The clinkering of the ash is largely a matter of chemical 
composition. Strictly speaking it depends on the com- 



114 



American Malleable Cast Iron 




Fig. 55 Picking table in a coal tipple, showing facilities for removing 
slate, sulphur, etc., by hand. 




Fig. 56 Adjustable loading boom which places coal in car without 

breakage 



Fuel and Refractories 115 

pounds formed in the ash under the temperature and chem- 
ical conditions existing in the fuel bed. Therefore, analyses 
made on laboratory preparations of as-h are not correct state- 
ments of what may happen in the fuel bed, but are of some 
value as indicating what may be expected. An ash of a 
very satisfactory fuel had the following composition : 



SiO 2 


Per Cent 
44 52 


A1 2 O, 


43 75 


Fe.O, 


1 32 


CaO 


5 72 


MgO 


. . . . 1 05 


Na 2 O 


) 


K ? O 


. ( 3.64 



The analysis is of a laboratory preparation of the ash. 
On the grates the Fe,O 3 would be largely reduced to FeO. 

The fusing point of the ash of eastern coals is 2400 to 
2850 degrees Fahr. Above 2600 degrees Fahr. is preferable. 

In general, the absence of iron oxide, alkalies and lime 
in the order given is considered a desideratum. 

The ash and sulphur contents of coal are considerably 
affected by the method of preparation and in recent years 
mining conditions have been such as to make for a steady 
deterioration along these lines. 

Air furnaces require a lump coal for their fuel 'but com- 
mercial practice varies as to the size of screen over which 
the coal should be passed before shipment. Some foundry- 
men desire coal not finer than that which will not pass a 
4-inch mesh, while others tolerate all that will pass over a 
^4-inch screen. The beslt practice probably is a little nearer 
the latter figure than the former say about 1^2-inch screened 
lump. 

When fuel is to be burned in pulverized form in melt- 
ing furnaces the quality of coal required is the sam'e as for 
direct combustion on the grates, except that the smaller 
sizes of coal can be utilized. 

A number of engineering concerns have developed 
highly specialized plants for grinding and pulverizing coal. 
The sequence of operations in all of them is substantially the 



116 



American Malleable Cast Iron 




d 

o 
be 
rt 

be 

S3 

o 



be 



Fuel and Refractories 117 

same. The coal, crus'hed to fairly small size or purchased 
after screening, passes through a device where it is dried by 
a current of warm air. A favorite method is to feed it in at 
one end of a rather long narrow cylinder rotating on its 
axis, whic'h is slightly inclined to the horizontal. As the 
cylinder revolves the coal rolls over and over and travels 
toward and finally out of the lower end of the cylinder. A 
current of warm air passes through the cylinder, usually in 
the direction opposite the flow of coal. 

From the end of the dryer the coal is automatically de- 
livered to a grinder, one type of Whic'h consists of an ar- 
rangement like the "fly balP' or centrifugal governor of a 
steam engine. The weights are in the form of rollers whic'h 
run against a surrounding ring when the mechanism is ro- 
tated. The fuel is ground to flour between these rollers 'and 
the ring, but if any hard lump such as a piece of scrap iron 
should fail to have been removed it merely crowds through 
between the roller and track and does no damage. 

Means are usually provided for screening or otherwise 
separating insufficiently ground material and returning it to 
be reground.- The product should be reground to pass a 100- 
mesh sieve and 75 per cent to pass a 200-mesh sieve^ When 
ground to size it is transported by belt or screw r <5onveyor 
to bins. A pulverizing plant is shown in Fig. 92. 

In -general it is well to store only limited qu#fitities of 
ground coal- -'owing to the fire hazards. Dried pulverized coal 
absorbs moisture readily, and sticks together and^feeds to 
the 'burner in a lump condition if it has an opportunity to 
take up water before being used. 

The transportation of coal dust by carrying it in a cur- 
rent of air is dangero ; us, the mixture being highly explosive. 
In the best installations the air and coal are mixed just as 
near the point of fen fry- into the furnace as possible to min- 
imize the danger. 

Gas as a fuel is only an indirect application of the com- 
bustion of coal, indeed it might well be maintained that any 
use of coal for this purpose involves its gasification even 
though that process may be carried out in the fire box in- 
stead of in a separate apparatus. 



118 



American Malleable Cast Iron 




be 





Fuel and Refractories 119 

Gas fuels are classified as illuminating gas or producer 
gas. The former is either a distillation product of coal, or a 
mixture of hydrogen, carbon monoxide and hydrocarbons, 
called water gas and made by the action of steam on red 
hot coke. Producer gas is a mixture of carbon monoxide 
and hydrogen. 

Illuminating gas is too costly for extensive metallurgical 
operations. Its use is limited to crucible furnaces for brass 
melting, etc., and small core ovens. If the gas is a by-prod- 
uct in the manufacture of coke, it is commercially available 
and then only in the plant operating the coke ovens or in 
neighboring plants. If the gas is to 'be piped any distance it 
can generally be more profitably sold for public consump- 
tion for domestic requirements. 

The operation of a gas producer is simple in principle. 
A gas producer is merely a firebox in which a deep bed of 
fuel is burned with a limited supply of air, the intention 
being to burn the carbon of the fuel to carbon monoxide. 

Theoretically, the producer gas is air in which the oxy- 
gen has been converted to carbon monoxide and should con- 
tain about one-third carbon monoxide and two-thirds nitro- 
gen. In practice the water from the combustion of the hy- 
drogen of the fuel, the moisture of the fuel itself and the 
steam which is introduced with the air supply to avoid 
clinkering all react with carbom, liberating some hydrogen. 
Also the fuels rich in volatile matter distill off more or 
less hydrocarbon gases. Furthermore, if the fuel bed is 
allowed to get uneven permitting air to come through, some 
of the carbon monoxide is burned to dioxide. The latter 
constituent is more prevalent in producers blown with steam 
than in those blown with air alone. 

As a general statement of the composition of commer- 
cial producer gas, the following figures are quoted from Wyer: 

Table III 

COMPOSITION OF PRODUCER GAS 

H CH 4 C 2 H 4 N CO O C6 a 

Gas from hard coal 20.0 .. .. 49.5 25.0 0.5 5.0 

Gas from soft coal 10.0 3.0 0.5 58.0 23.0 0.5 5.0 

Gas from coke 10.0 .. .. 56.0 29.0 0.5 4.5 

Gas air blast 4.43 .. . . 62.12 33.04 .. 0.41 

Gas same as above with air 

and steam blast . . 14.00 53.3 27.2 5.5 



120 American Malleable Cast Iron 

The CO 2 values are rather high, an attempt usually be- 
ing made to hold CO 2 to 3 per cent. 

It is obvious that the 'heat value of the gas from a pound 
of coal cannot be greater than the heat value of the original 




Fig. 59 Cross section of a modern gas producer 

pound of fuel. The combustion of carbon to CO liberates 

4450 
or roughly 30 per cent of the heat of combustion of 

carbon to CO 2 . This heat is transmitted to the incoming 
fuel and to the products of combustion as well as to the 
producer structure. It finally leaves the producer by radia- 



Fuel and Refractories 121 

tion from the walls and also as the sensible heat of the gas. 
it therefore is of advantage, except in open hearth practice, 
to make the gas as near the furnace as possible to avoid the 
loss of 'heat units by coo. ing the gas stream in passing 
through long ducts. 

Where the gas is to be widely distributed or burned in 
small accurately controlled burners a cleaned gas from which 
tar and heavy hydrocarbons have been removed is desirable. 

As stated before, gasification adds nothing to the heat 
value of the fuel ; it may, however, result in heat economy 
due to the better control and more economical combustion 
conditions possible with gas fuel as compared with solid 
fuels. 

Producer gas being a fuel of rather low calorific power 
usually is burned with hot air. The use of cold air does 
not give sufficiently hot flames for melting operations ; in- 
deed the temperature m'ay not be high enough to maintain 
combustion unless a warm or hot air supply is provided or 
the gas itself be fairly hot. 

Producer gas usually is made from bituminous coal, al- 
though wood, peat, lignite, coke and anthracite can be used. 
The requirements for producer gas fuel in general are simi- 
lar to those for >air furnace fuel. The coal should be rea- 
sonably low in ash and the ash should not clinker. The 
coal must not soften or swell on heating and preferably 
should be low in moisture and high in volatile matter. Fur- 
ther, it should be fairly uniform in size and, for melting op- 
erations, low in sulphur. However, there are many bitumin- 
ous coals giving good results in producers which do not 
work satisfactorily in the air furnace. 

Coke is used as ; a metallurgical fuel in the malleable 
industry in cupola practice only. As everyone knows, it is 
gas 6r similar coal from which the volatile matter, includ- 
ing moisture, has been distilled in retorts, beehive ovens or 
by-product ovens. It contains all the ash in the coal from 
which it was made and is therefore from 50 to 100 per cent 
higher in ash than gas coals. The remainder of the coke is 
practically pure carbon. All coke contains sulphur and 
there is a general feeling 1 in favor O f foundry cokes con- 
taining less than 1 per cent of this element. Sulphur is 



122 



American Malleable Cast Iron 







Fuel and Refractories 123 

taken up by the metal more readily in cupola practice than 
in the air furnace, owing to the fact that fuel and metal 
come into actual contact with each 'other. Moreover coke 
must not be too fine and must be fairly strong to make a 
suitable fuel. The ash should be as low as practicable and, 
if possible, siliceous in character, since it is easier to add 
basic materials to flux with the ash than to add acid 'materials. 

The as'h is similar in composition to that of coal and 
corresponds to low grade fire clay. Cupola fuel is not of 
great interest hi this discussion, owing to the general aban- 
donment of cupola malleable. In the case of electric fur- 
nace practice in which cupola metal is the raw material for 
the electric furnaces it is, of course, an important material. 

Oil is found rather widely distributed throughout the 
country. Fig. 53 shows the oil areas, exclusive of oil shales. 
Oil has many advantages as a fuel, including cleanliness, rel- 
ative freedom from sulphur, convenience of distribution and 
accuracy of control of combustion conditions. 

Twenty or 30 years ago it was customary to burn local 
crude oils just as they came from the ground. The need for 
gasoline and lubricating oils has caused the abandonment of 
this practice and today the fuel oil used consists of the 
residue remaining after the distillation of the commercially 
important products. Nearly all the petroleum products are 
hydrocarbons of the methane series having the general 
formula 

C r H 2I1 + 2 

All have nearly the same 'heat value per pound, because 
n being a fairly large quantity, the atomic ratio of carbon to 
hydrogen is in all of them very nearly 1 to 2 corresponding 
to a ratio by weight of 6 to 1. The more volatile com- 
pounds such as gasoline, kerosene, etc., are the members of 
low molecular weight in which n is from 5 up. 

Fuel oil has been applied to 'annealing furnaces very 
conveniently. It is a useful fuel in open-hearth practice and 
has been successfully used in that connection in the malle- 
able industry. Under favorable circumstances it can some- 
times compete for this purpose with producer gas -and pul- 
verized coal. Furthermore, it is easy to arrange open-hearths 



124 American Malleable Cast -Iron 

to permit the use of either oil or gas or oil or pulverized 
coal, which is a convenient arrangement. 

Attempts have been made to burn fuel oil in air fur- 
naces. No particular difficulty exists in actually doing the 
melting, but generally the process has not been either eco- 
nomically or metallurgically successful. J. P. Pero reports* 
what he regards as satisfactory results at an Illinois plant, 
but even there it is admitted that excessive oxidization losses 
were not overcome and 'the fuel cost was high. A plant in 
Michigan is said to 'have operated successfully with oil melt- 
ing, even at a high unit cost for fuel. The details are not 
available to the writer. 

Natural gas is actually the first member of the petro- 
leum series methane CH 4 , corresponding to n=l. It is 
found associated with petroleum. Its rapid exhaustion by 
wasteful use is one of the scandals of our economic system. 
It formerly was used for annealing. 

There remain for consideration '-the raw materials which 
are grouped under the heading of refractories. These mate- 
rials include molding sand, fire sand, fire clay, fire brick and, 
to 'a limited degree magnesite, magnesite 'brick, silica brick, 
dolomite, gannister and sands'tone. 

Molding sands are somewhat widely distributed in na- 
ture and -consequently each plant generally uses a local sand. 
Molding sands are generally derived from granite which has 
weathered and are frequently found in glaciated areas. Mold- 
ing sands differ among themselves and each purpose requires 
a sand of specific characteristics. 

In the malleable foundry a sand is desired consisting of 
well rounded quartz grains, of nearly- uniform and fairlv 
small size, coated evenly with a moderate amount on\y of 
fairly plastic but also reasonably refractory clay. The actual 
size of grain and amount of clay desired will vary with the 
character of the work. The heavier castings require coarser 
and clavier sands than the lighter. 

The uniformity of grain size and -roundness of grain 
are desired in order to give the greatest possible opportun- 
ity for the g-as to escape from the molds. If too much clay 

*Vol. XXVIIT. p. 316, Transactions. American Fonndrymen's asso- 
ciation. 



Fuel and Refractories 



125 







Fig. 61. Operations in a molding sand pit 

is present or if the 'Sand consists of grains differing largely 
in size the clay or small silica grains partly obstruct what 
should be openings between the grains. 

The clay is needed 'to hold the sand in place. The silica 
grain is very refractory, so that the refractoriness of the 
sand depends upon the property of the clay coating. If the 
clay contains lime or iron oxide the refractoriness is much 
decreased. Most sands contain vestiges of feldspar from 




Fig. 62. Hauling sand from a pit 



126 



American Malleable Cast Iron 




be 




Fuel and Refractories 127 

the original granite and these sands are relatively easily 
fusible. 

The analysis and screen test of sand does not furnish 
a good guide to its usefulness, as they are difficult to in- 
terpret. 

The United States bureau of standards and the Ameri- 
can Foundrymen's association have gathered extensive data 
w'hich are available to the interested reader. 

Tests for porosity, strength of bond, imperviousness and 
fusibility are more valuable, but a discussion of these proper- 
ties and their relationships would be too technical to interest the 
general reader and in the present state of our knowledge 
would be largely speculative. 

Frequently sand free of clay is wanted in coremaking, 
the binder furnishing all the cohesion desired and preventing 
cores growing too hard, due to the burning of the clay. For 
such purpose wind-blown lake or sea sands, nearly pure 
quartz, are generally used. 

Fire sands are very pure silica sands usually in uniform 
rounded grains. They seldom contain over 2 per cent of im- 
purities and are used for the bottoms of acid open-hearth 
and air furnaces. The presence of a small amount of basic 
material is required to cause the sand to sinter properly. 

Sandstone is a naturally compacted mass of silica sand 
occasionally used in cupola and other furnace linings. Gan- 
nister is a siliceous sedimentary rock of highly refractory 
character used in furnace linings usually in crushed form. 

Fire clays are refractory silicates of aluminum occurring 
in nature. They contain as impurities oxides of iron, cal- 
cium and the alkalies as well as some of the rarer metals. 

The very pure and refractory flint clays possess little 
plasticity. Other varieties are more plastic and also more 
fusible. Fire clay is seldom used alone, being mixed with 
water and crushed fire brick or silica sand to form a mate- 
rial for patching furnace walls. Fig. 63 shows the location 
of the principal supplies of molding sand and high grade fire 
clay in the United States. Clay fire brick, made from fire 
clay usually at or near the source of clay, consist merely 
of mixtures of refractory and hard flint clays, ground fire 



128 



American Malleable Cast Iron 




jS^^v ^jH^S; 



$m 



Fuel and Refractories 129 

brick, ground gannister and a plastic fire clay formed into 
shapes and burned at high temperatures. 

The manufacture of fire brick is one of the most im- 
portant ceramic industries and cannot be more than casually 
referred to here. Brick differs in the material used, the 
fineness or coarseness of grind, the density to which the ma- 
terial is compressed and the temperature at which it is 
burned. 

The material used -largely determines the refractoriness or 
melting point. Fine grained, fairly dense and not too hard 
brick possess great strength. Coarse, open, lightly burned 
brick resists rapid changes of temperature. Fine, dense, hard 
burned brick resist penetration of slags, hence every use has 
special requirements. A noteworthy feature is that all clay 
brick shrink when first heated. 

Fire Clay Refractories for Malleable Iron Works 

The chief deposits of high grade flint fire clays are lo- 
cated in Pennsylvania, Kentucky and Missouri. These clays 
are formed from the weathering of feldspar and feldspathic 
rocks which have the formula K 2 O, A1 2 O 3 6 SiO 2 . Pure 
kaolins should be A1 2 O 3 2SiO 2 , 2H 2 O, the potassium silicate 
having been dissolved. The flint fire clays approach this 
pure clay or kaolin in chemical composition except that they 
contain some iron oxide 'which gives the burnt product a 
yellow tint. They are a secondary or transported clay de- 
posited in still water and are found in the carboniferous 
areas or coal measures. 

Where the coal is thick the clay is generally thin, and 
when the coal 'thins out to almost nothing the clay thickens 
up to workable deposits eight to 20 feet in thickness. 

These flint clays usually are mined in the Pennsylvania 
and Kentucky districts, also occasionally in Missouri, but 
the Missouri flint clays often lie in pockets. In certain dis- 
tricts, such as at Mexico, Missouri, extensive deposits are 
worked 'by stripping the overburden and then mining in an 
open pit. 

The following chemical analysis of raw clay and burnt 



130 



American Malleable Cast Iron 




Fuel and Refractories 131 

bricks will illustrate typical compositions for malleable fur- 
nace work: 

Table IV 

BURNT BRICK ANALYSES 

Pennsylvania Missouri Kentucky 

SiO 3 53.05 55.29 54.41 

A1 2 O 3 41.16 40.18 . 36.20 

Fe 2 O 3 2.65 2.44 2.10 

TiO, 1.80 0.00 0.00 

CaO 0.00 0.00 2.13 

MgO 0.00 0.71 5.16 

Alkalies' 1.34 0.76 9.39 

Fluxes 5.79 3.91 

Cones 32-33 34 31 

Ram' Clay Analysis Missouri Flint Clays 

Per Cent 

Loss on ignition 12.66 

Si0 2 49.08 

Al,0, 35.67 

Fe 3 O 3 1.28 

CaO -. 0.00 

MgO .:.... 0.63 

Alkalies , ., 0.68 

Fluxing parts , , -...,.;; 2.59 

Free silica 7.6 

The clay is ground and screened in a dry pan in some' 
plants while others put the raw clay in a wet pan and add 
excess water making the clay plastic and then introduce the 
correct per cent of coarse grog, chamotte or calcine. The] 
latter is simply burnt clay crushed to coarse .sizes 'help 
take care of strains occurring in brick in malleable iron 
practice. 

The clays are all pugged in a wet pan as this process 
develops the greatest placticity. This mud is carried to the 
molder who works up portions of it into long (soft mud) 
bricks and then throws them with great force into the molds 
which are bumped several times to cause the clay to fill the 
molds and give good sharp corners. These brick then are 
carefully dried on a steam-heated floor. 

In a num'ber of plants and for certain purposes brick 
instead of being molded as described are pressed hard be- 
fore drying giving increased density. 

When thoroughly dried the brick are trucked to kilns 
where they are set as shown, Fig. 67, leaving spaces for 
heat and draft. The kilns are down draft, fired with coal, 



132 



American Malleable Cast Iron 




Fuel and Refractories 133 

natural or producer gas, the gas being used more on con- 
tinuous kilns. 

Silica brick, used for very high temperatures, as in the 
roofs of open-hearth and electric furnaces, is a brick made 
like a clay brick in which the material is nearly all silica, 
using only enough clay to permit the brick to be burned to 
hold together. They are very hard, very dense, and possess 
an enormous coefficient of thermal expansion. They are 
strong, almost infusible, but will not withstand sudden tem- 
perature changes. 



ft W 

Hi l| ! 

::. ~ -^t, S-^W- ~ W^ W^*: ju^fr., M 







Fig. 67. Firebrick and special fireclay shapes in a kiln ready to be 

burned 

Magnesia consisting of MgO, obtained by heating the 
mineral magnesite, whic'h is MgCOa, to expel the car'bon 
dioxiide, is used both ground and as brick in basic furnace 
linings. In the malleable industry it is used only in electric 
furnaces. It is very refractory and resists basic slags. It 
conducts heat readily and must be backed up by a layer of 
clay brick if heat losses are to be made a minimum. It has 
relatively little strength. 

Dolomite, a double carbonate of calcium and mag- 
nesium, is used in electric furnace bottoms. It is burned 
before use, resulting in a mixture of CuO-f-MgO in the ratio 
of about 1.4 to 1.0. The commercial preparations may contain 



134 American Malleable Cast Iron 

from 8 per cent to 25 per cent of other oxides, namely SiCX, 
A1 2 O 3 , and Fe 2 O 3 . Some producers purposely add iron oxides 
(or silicates) feeling that the material then deteriorates less in 
storage and sinters better. 

Chromite, zirkite, and bauxite, oxides of chromium, of zir- 
conium, and of aluminum respectively, possess no commercial 
significance in the malleable industry, although they are well 
known refractories. Carborundum, silicon carbide, is another 
refractory which has not found application. 



VII 

AIR FURNACE MELTING 

THE air furnace is the commonest device employed for 
melting malleable iron, having supplanted the cupola 
on the score of quality and the crucible furnaces of 
early days on the score of production and economy. 

The air furnace is of the reverberatory type in which 
the metal, in the form of a fairly shallow bath, is melted by 
the flame from fuel burning in a firebox at one end of the 
hearth. The flame is drawn over the hearth by a stack at 
the opposite end from the firebox. In the earliest type, the 
stack was at one side with a charging door at the end op- 
posite the firebox. The present arrangement is similar in 
character to that of a puddling furnace. 

The early air furnaces were very small; some of the 
first are said by Davis on the authority of George Belcher 
to have had capacities of 800 or 1000 pounds, a 1500-pound 
charge being viewed with alarm. Modern furnaces 'have 
been, continually growing in size, and now five-ton heats 
are unusual, capacities from 10 tons to 15 tons being most 
common in practice. Furnaces have been built and oper- 
ated with capacities beyond 30 tons, but there are relatively 
few in use with capacities far above 20 tons. 

Design Is Simple 

The construction of an air furnace is relatively simple. 
Fig. 68 shows an air furnace in side elevation and cross sec- 
tion. 

The furnace walls are of fire brick, usually 13 to 18 
inches thick, supported and enclosed by cast iron side and 
end plates about 1 inch thick. The 'bottom or the hearth 
A is built of silica sand or more. rarely paved with fire brick. 
Coal is burned in the firebox B, the air being forced through 
the fire by a blower discharging into the ash pit C '; the ash pit 
doors D being kept closed. Air is also admitted through the 
tuyeres E to complete the combustion of the gas and flame com- 
ing over the front or fire bridge Avail F. The roof of the 



136 



American Malleable Cast Iron 



.;^y>'^l 




Air Furnace Melting 137 

furnace consists of a series of removable fire brick arches, 
or bungs, supported in cast iron frames. A sufficient number 
of these are removed to permit the introduction of the melt- 
ing stock. 

When charging the furnace, the sprue to be melted is 
introduced first in the form of a. layer of fairly uniform 
thickness extending nearly the full length of the hearth. 
On this is placed malleable or steel scrap, the latter usually 
being kept well forward toward the front bridge wall. Pig 
iron is placed on top of this in two piles, one well forward, 
the other further back. 

Most well designed furnaces are of such dimensions as 
to be nearly full to the roof when a heat of normal size is 
charged. Care therefore must be taken to leave an oppor- 
tunity for the free passage of flame from F to the rear 
bridge wall. 

The bungs are then put on and firing commenced. The 
iron soon begins to heat, naturally first at the top and in 
front. The firing is so conducted as not to cause much melt- 
ing to occur until the lower part of the charge is well 
heated through to a gO'od red. 

Of the ingredients in the mix, sprue has the lowest 
melting point, pig iron next, then malleable scrap, and steel 
the highest. The melting points vary inversely as the com- 
bined carbon, although the conclusions are slightly compli- 
cated by the reabsorption or recombination of the carbon of 
malleable scrap below the melting point. 

Through the courtesy of H. W. Highriter, the author 
has been furnished data as to the recombination of carbon 
in pig iron when heated under circumstances comparable 
with melting conditions. The data 'have been shown graphi- 
cally in Fig. 69. Highriter observes a rapid increase in combined 
carbon at the expense of graphitic carbon above 2000 
degrees Fahr. The author has calculated the temperature of 
the solidus for the observed combined carbon and plotted 
these temperatures in a dotted line. When this temperature 
falls below that of the specimen, incipient fusion has com- 
menced. Melting is complete when the temperature reaches 
the liquidus which is dependent on the total carbon and 
calculated by Highriter as 2372 degrees Fahr. The metal by 



138 American Malleable Cast Iron 

observation fused at 2362 degrees Fahr. It will 'be observed 
that the melting point referred to by the author is that 
where melting is begun, above this temperature presumably 
the graphite is rapidly destroyed by solution. 

Moldenke many years ago published data as to the re- 
lation between combined carbon and melting point of cast 
iron and Dyer* refers to the same facts. 

In interpreting the author's statements, and presumably 
Moldenke's and Dyer's, confusion between the beginning 
and completion of melting must be avoided. 

If the firing is properly managed, it is not necessary to 
melt the steel, the molten pig iron dissolving the steel as it 
runs down before the steel actually melts. Some melters ad- 
vocate introducing the steel only after the rest of the charge 
is melted. 

The sprue melts fairly, readily even under all the other 
material due to its high combined carbon content. As the 
iron melts the surface oxidizes so that there results both liquid 
iron and liquid iron oxide, probably Fe 2 O 3 . The latter floats on 
top of the former and reacts with the carbon, silicon, and 
manganese of the metal, oxidizing those to CO 2 , CO, SiO 2 and 
MnO and being itself reduced to FeO almost or quite com- 
pletely. 

The oxides of manganese and iron combine with the silici 
to form an acid silicate which also dissolves some of the 
refractories in the furnace lining. The resulting slag .soon 
covers the surface of the molten metal protecting it from 
further action of the furnace gases. 

As pools of iron covered with slag form, a good melter 
will endeavor to roll unmelted pig iron and steel into these 
pools so as to bring the entire charge under the slag blanket as 
soon as possible, thus minimizing oxidation losses. 

The flame conditions also are carefully regulated by atten- 
tion to the dampers in the blast lines to the firebox and top 
blast tuyeres and by keeping the openings over the bridge walls 
and the channel or neck H to the stack of the right dimensions. 

When the charge is all melted it is well mixed by rabbling 
with a skimmer bar. The slag is then skimmed off by raking 
*lron Age, Nov. 17, 1921. 



Air Furnace Melting 



139 



it out through the skim holes, the skimmer bar consisting of a 
1-inch iron bar having a flat plate, say % x 3 x 9 inches 
affixed by its center to the end of the round bar. The other 
end of the bar is bent into a ring to form a handle. 

Meanwhile the fire is being constantly worked with a 
poker to keep up active combustion. The heat has to be skim- 
med at intervals in order to make rapid heating possible 




Fig. 69. Graph showing recombination of carbon in pig iron 

and also to keep the final product fairly clean. One producer 
does not remove the slag, but drains it off after the metal 
has all been run -out of the furnace. 

The progress of the heat is judged as to temperatitre and 
composition by 'the inspection of a freshly broken surface of a 
not too rapidly cooled ' sample and of the molten metal in the 
ladle. For satisfactory work a knowledge of the composition 
of previous heats also is necessary. In a few plants more or 
less complete preliminary analyses are attempted before tapping. 
This chemical practice is attended with a certain amount of un- 



140 



American Malleable Cast Iron 




Air Furnace Melting 141 

certainty as to further changes of composition between sampling 
and tapping and is therefore less effective than the correspond- 
ing practice in electric melting. When the metal is hot and of 
proper composition the clap stopper in the tap hole / is cut 
through and the metal runs out in a stream into the molders' 
ladles. 

In the early days of the art the profile of the furnace 
roof longitudinally was given very complex, almost fantastic 
curves. These usually had a sharp dip in the roof just beyond 
the front bridge, then a rise forming a sort of hump over the 
hearth, then a drop toward the rear bridge. wall and then a rise 
directed toward the stacks. 

Furnaces of the older type had sloping roofs but recently the 
tendency has been toward a nearly straight roof, lower at the 
rear bridge than at the front and sometimes rising again into 
the stack as a matter of convenience. A modern design is 
shown in Fig. 70. 

The flame in flowing through the furnace obeys laws 
similar to those governing the flow of water in channels. 
These laws 'have been completely investigated by Crum-Grzimai- 
lo of Petrograd, (Stahl und Eiscn, Dec. 7, and 11, 1911), who 
developed the mathematical formulae and coefficients applying 
to the problem in great detail. The discussion is much too 
technical in character to be even abstracted here beyond the 
statement that the laws are those which would apply to the 
flow of one fluid through another, if the two were not mixable 
and differed in density as does the hot flame and cold at- 
mosphere- 

This investigation coupled with a knowledge of combustion 
and temperature conditions to be expected forms the only logi- 
cal basis for furnace design. In practice actual furnace design 
is generally based on modifications of previous designs. This is 
in many respects sound policy as tending to avoid erratic prac- 
tices. On the other hand, there is a great tendency toward per- 
petuation of obsolete features inherent in such a process of ev- 
olution. 

An inspection of the designs of many furnaces shows a 
wide variation on some apparently vital points. These dif- 
ferences, however, are not always as little justified as may 



142 



American Malleable Cast Iron 



appear on the surface for the viewpoint of different designers 
may not be the same. 

Thus, for example, it is undoubtedly sound metallurgical 
practice to make but one heat a day on a furnace and make 




Fig. 71. A waste heat boiler connected to two air furnaces. Note that 
coal for auxiliary firing is on hand 

that a very large one, for ithe brger the capacity the greater 
is the melting economy, other things being equal. On the 
other hand, consideration must be given to the space re- 
quired for molds, to the physical ability of the men to pour, 



Air Furnace Melting 143 

etc- Thus it is that this practice may not be feasible. If 
heats are required at given time intervals it may be more 
important to keep the time schedule correct than to get the 
maximum of economy, hence fuel consumption may be sacri- 
ficed to melting speed. Such a consideration also may limit 
the practicable size of heat. Also many furnaces are built 
in existing buildings, or under other conditions which handi- 
cap the designer by limiting him to certain dimensions from 
these causes. 

A general idea of the usual dimensions of air furnaces 
can be gained from the following: The volume of the hearth, 
(the volume of the basin below the level of the skim holes) 
is directly dependent on the amount of metal to be melted 
and is not subject to any discretion. One pound of melted 
cast iron, together with its accompanying slag occupies about 5 
cubic inches; therefore 10,000 cubic' inches of hearth must 
be provided for each net ton of furnace capacity. 

There are certain practical limits to the depth of molten 
metal in the hearth which can be successfully worked. Shal- 
low baths presenting to the flame a large surface per unit 
weight of metal, heat easily and quickly but also oxidize easily 
and quickly. Extremely deep baths are difficult to heat, but the 
great weight per unit of surface favors the rapid transfer of 
heat from flame to metal per unit of hearth area. 

Moreover, large capacities coupled with shallow baths may 
involve impracticable dimensions. Again, the bottom of the 
furnace must have sufficient slope to assure. complete drainage 
to the tap hole. Even in unusually short furnaces this slope 
produces a difference in depth at the tap hole and rear 
bridge of perhaps 5 inches so that an average depth of less 
than 2 l / 2 inches is not workable in any event, because it neces- 
sitates a "feather edge" of metal next the bridge. 

In practice the average depth of metal ranges from about 
5 to 9 inches, the greater depths usually occurring in furnaces 
of the greater capacities. The depth at the tap hole may be 
from 2 l / 2 to 5 or 6 inches greater than the average depth de- 
pending largely on the furnace length. These depths correspond 
to hearth areas running from about 13% square feet per ton 
down to less than 8 square feet per ton. 



144 American Malleable Cast Iron 

The requirements of firing, skimming, etc., as well as the 
maintenance of roof arches sets a maximum inside width of 
between 5 and 6 feet for air furnaces of the usual design, a 
few large furnaces of special design have a clear width of 7 
feet. When the maximum width is reached the capacity of the 
furnace can be increased only by increasing the hearth length. 
Extremely shallow baths are impracticable when large capac- 
ities are desired because they necessitate long furnaces- For 
example, 2Oto>n furnaces with a hearth area of IS 1 /-* square 
feet per ton would be about 45 feet long between the bridge 
walls. Hearths from 14 to 27 feet long are in common use, 
and in a few unusually large furnaces they are several feet 
longer. A certain length of hearth is desirable because it 
insures a better contact of flames and charge. Excessive lengths 
cannot be had with small capacities as the furnace would be 
too narrow. The practicable length also depends on the fuel 
and firing conditions since a length which does not allow the 
flame to reach to the rear bridge wall is unworkable. 

The firebox is almost f of necessity of the same widths as 
the hearth. The grate area required depends on the rate of 
combustion of fuel desired and this in turn depends on the 
furnace capacity and on the relative importance of quick as 
against economical heating. Air furnace grates burn from 43 to 
77 pounds of coal per hour depending on firing' conditions. 
Values of from 67 to 77 pounds are more common than those 
near the lower limit. 

Reported tests indicate that air furnaces use from slightly 
under 500 to about 1200 pounds of coal per ton of charge. 
These are extreme ranges* the usual commercial range being 
from 750 to 900 pounds per ton, depending largely on the size 
of the furnace- These figures give some indication of grate 
areas required under various conditions, having in mind also the 
fact that an attempt to melt rapidly is often uneconomical. 
It seems to be usual practice to provide from 2 to 21/2 square 
feet of grate per ton of charge although a number of fur- 
naces exceed this rate. 

Many designers do not agree on the correct height of an 
air furnace roof. From 15 to 17 cubic feet per ton from 



Air Furnace Melting 145 

hearth to roof are unavoidably necessary in order to accom- 
modate the unmelted charge. This sets a minimum of height 
for any given hearth area per ton of charge. 

Quantity of Air Varies 

Almost invariably the roof slopes downward toward the 
rear bridge. The old humpback furnaces had a somewhat great- 
er average height than the more modern straight-roofed 
furnaces. The average height of roof above the metal at 
the side walls is about 24 inches. A pound of ordinary melt- 
ing coal requires about 12j4 pounds of air for combustion under 
usual operating conditions. The relative amount of air entering 
the furnace through the top blast tuyeres and through the 
grates varies in practice, but the average ratio seems to be 
about 28 to 100. Therefore a pound of coal requires about 
10 pounds of air through the grates and 2j4 pounds of air 
through the top blast in ordinary operating practice. 

The firebox is operated so that it produces a poor grade 
producer gas which is then burned with a sufficient amount 
of air for theoretical combustion. A typical gas leaving the 
firebox is composed of 1.2 per cent oxygen; 8.0 carbon dioxide; 
12.1 carbon monoxide; and 78.7 per cent nitrogen. The gas 
leaving the stack contains 1.1 per cent oxygen; 12.7 carbon 
dioxide ; 3.6 carbon monoxide ; and 82.6 per cent nitrogen. The 
analyses take no account of the water from the combustion 
of the hydrogen of the fuel. The oxygen in this water and 
that used in the oxidation of silicon and manganese account 
for the relatively high value of the nitrogen. The flame gases 
also contain unburned hydrocarbons of unknown character and 
amount which escape sampling. 

Any attempt to further reduce the carbon monoxide content 
by adding additional oxygen, probably would result in a pro- 
hibitively high excess of oxygen in the gas, causing heavy 
oxidation during the melting process. 

The mechanism of this oxidation has already been re- 
ferred to as consisting of the oxidation of the iron to the Fe 2 O 3 
followed by the subsequent reduction of the Fe 2 O 3 to FeO 
by the silicon, carbon and manganese of the bath. The amount 
of oxidation varies widely depending upon the furnace at- 



146 American Malleable Cast Iron 

mosphere and similar conditions. Over an extended period, 
however, it seems nearly constant for any successfully operat- 
ing plant. The losses expressed in percentage of the total 
weight of original charge and in percentage of the amount 
of each element present are generally about as follows: 

Table V 

LOSSES OF ELEMENTS IN MELTING IN AIR FURNACE 

Total amount 

Total charge of element 

100 -per cent 100 per cent 

Carbon 0.62 15.8 

Silicon 0.33 31.4 

Manganese 0.26 48.1 

Phosphorus 0.00 0.00 

Sulphur 0.01 22.2 

Iron 1.14 1.2 



2.37 

The results of the figures in the second column form an in- 
teresting comparison of the "oxidizability" of the different ele- 
ments when melted in an acid furnace. 

Oxygen Absorbed During Melting 

A more interesting method of clearly showing the relative 
affinity for oxygen of the different metals is to calculate the oxy- 
gen combined with each one of the elements during melting. 
This calculation has been made using the preceding data and 
the results are shown in the table below. In the first column 
is shown the oxygen combined with each of the four oxidiza- 
ble elements in terms of the weight of original charge and in 
the second column in terms of the weight of the oxidized ele- 
ment present in the charge. 

Table VI 

OXYGEX ABSORBED BY EACH OF THE OXIDIZABLE ELEMENTS DURING AIR 
FURNACE MELTING 

Element present in 

Total charge original charge 

100 per cent 100 per cent 

Carbon 1.60 50 

Silicon 0.38 36 

Manganese 0.06 11 

Iron ..... 0.32 34 

2.36 



Air Furnace Melting 147 

It will be seen that carbon combines much more greedily 
with oxygen than any other element, silicon coming next, man- 
ganese oxidizing much less readily and iron only slightly. Of 
course the results would differ with variations in gas com- 
position and furnace lining. 

It will be seen that the melting process oxidizes a total of 
2.34 per cent of the original charge, and combines there with 
oxygen weighing 2.36 per cent of the original charge. There 
should thus result a weight of slag equal to 2.5 per cent of the 
metal charged and of gas equal to 2.2 per cent of the metal 
charged, were there no contamination from molten refractories. 
A typical sample of air furnace slag showed the following com- 
position : 

Analysis of Air Furnace Slag 

Per cent 

FeO 28.80 

Fe 2 O 3 1.16 

MnO 4.85 

Si0 2 (etc) 50.42 

A1 2 O 3 14.77 

100.00 

The metallic oxides aggregate 34.81 per cent of the weight of 
the slag. From the preceding tables, this corresponds to 13.8 
per cent SiCX. Therefore the above slag consists of a mix- 
ture of 58.70 per cent oxidation products and 41.30 per cent 
molten refractories and since the weight of slag oxidation prod- 
ucts was computed to be 2.5 per cent of the weight of the 
charge the actual slag weight should be slightly more than 
4.2 per cent of the original metal charged into the furnace. It 
is not assumed that these data are absolutely correct but they 
furnish a fair guide to what may be expected in practice. 

Refractories Destroyed by Melting 

Since every ton of iron melted destroys 34 pounds of re- 
fractories by melting, it is evident that frequent furnace repairs 
are necessary. The furnace parts most strongly exposed to 
heat usually are relined at intervals of from 10 to 20 heats. 
The roof over the hearth lasts usually from 16 to 24 heats 
and the sand bottom from 10 to 20 heats. In one instance the 
writer saw a furnace make 34 heats without relining, and 



148 



American Malleable Cast Iron 






Fig. 72. Gray sprue; characteristic of high carbon and silicon and 

sometimes of low pouring temperature (full size) 

Fig. 73. Gray sprue showing white patches; characteristic 
of less but still excessive carbon and silicon. Note "in- 
verted chill," i.e. greater grayness near the surface 

than at center (full size) 

Fig. 74. Moderately mottled sprue; characteristic of carbon, silicon 
and temperature suited to small work (fulj size) 



in another saw a bottom last 120 heats as a result of careful 
attention. However, this record is believed to be exceptional. 

The charge going into the furnace can be computed by 
adding to the final composition wanted the expected melting 
losses and then arranging a mixture from the available melting 
stock conforming to these requirements- The process is one 



Air Furnace Melting 



149 




Fig. 75. Normal sprue for metal of the higher carbon ranges of 
specification metal in average work. Note leaf-shaped bright 

crystal facets radiating from center (full size) 
Fig. 76. Similar to Fig. 74 but lower in carbon. Note decrease in 

leaf-shaped crystals (full size) 

Fig. 77. Similar to Fig. 76 but quite low carbon. Note finely gran- 
ular fracture from which the leaf-shaped crystal has almost 

- disappeared (full size) 

Fig. 78. "High" iron, i.e. metal low in carbon, silicon and manganese; 

fracture granular -throughout and edge showing blowholes 

(full size) 



of simple arithmetic and the great mystery made of the matter 
by the older melters was not justified. 

However, the -skill of ' the melter is important in main- 



150 American Malleable Cast Iron 

taming furnace conditions so that the oxidation losses are uni- 
form and as small as practicable. The appearance of the flame 
in the furnace, the eddy currents in the bath and the appear- 
ance of the slag, whether viscous or liquid, indicate to the 
skillful melter what is going on in the furnace. Similarly the 
color and fluidity of the metal and the appearance of the frac- 
ture after cooling permit of close inferences regarding its 
composition. 

Interpreting Appearance of Fracture 

Among the more obvious indications of the fracture are 
the presence of graphitic areas or mottles indicative of too 
high a silicon or carbon or both, larger leafy crystals radiat- 
ing from the center indicating moderately high carbons de- 
creasing to very fine granular structures as the carbon falls 
to near 2 per cent. There also is the rim of fine blow holes 
and the spray of oxidizing iron arising from the surface of the 
metal in cases of "burnt" heats very low in silicon. 

The actual conditions are not even capable of illustration 
photographically since some of the fractures do not show up 
clearly except by looking at them in light falling in various 
directions. 

It can be shown that by far the largest part of the oxida- 
tion losses, occurring in practice, is complete, when the metal 
is melted down and ready to skim. 

From the time the iron is all melted, before skimming, un- 
til the moment of tapping no marked changes of composition 
occur as to carbon and manganese although the silicon will 
decrease perhaps 0.1 per cent during the removal of the first 
slag. This presupposes a properly operated furnace. 

Composition May Vary During Heat 

Samples taken from the last of a heat frequently show 
a considerably lower carbon, silicon and manganese content 
than those taken at the first of the heat. However, this is due, 
not to a progressive oxidation which would have affected the 
entire heat to that extent had it been left in the furnace, but 
to the effect of oxidation on the very thin layer of metal 



Air Furnace Melting 



151 



left in the furnace as the last metal is being withdrawn. Only 
a small weight of metal is of a composition different from 
the bulk of the heat. A feature that frequently is misunder- 
stood is the elimination of graphite. Often it is supposed 
that the fact that the longer the heat is left in the fur- 




Fig. 79. Changes of metal after tapping 

nace the lower the graphite is due to oxidation of carbon and 
silicon. As a matter of fact the elimination of graphite is 
largely a function of the pouring temperature and time, and 
metal will show progressively clearer fractures during the 
progress of the pouring of a heat without any accompany- 
ing change of ultimate chemical composition. Fig. 79 shows 
such a condition. 

In this figure the composition of the metal with respect 
to total carbon, graphitic carbon, silicon and manganese is 



152 American Malleable Cast Iron 

shown for samples in the form of 1^-inch sand-cooled cyl- 
inders poured at intervals of three minutes each while the heat 
was running out of the furnace. It should be said in ex- 
planation that this was not a normal malleable iron heat but 
one for a special class of work requiring great perfection 
of surface on castings on thin sections, hence the high values of 
silicon and carbon. However, the curve shows strikingly the 
rapid decrease in combined carbon as the metal is exposed longer 
to high temperatures. 

Temperature of Furnace 

Temperature conditions in air furnaces are not accurately 
established. The metal flowing from the spout has a tem- 
perature from 2100 to 2500 degrees Fahr, as measured by 
radiation pyrometers. Such determinations involve a correction 
for coefficient of radiation since clean metal does not radiate heat 
as rapidly as would a theoretical black body. The use of optic- 
al pyrometers involves a similar correction for emissivity which 
is however of much smaller magnitude. Optical pyrometer 
measurements coupled with observations of metal at known 
temperatures suggest that true values are probably more nearly from 
2500 to 2700 degrees Fahr. and that the radiation coefficient 
is not well established. The flame in the neck when the 
heat is melted has a temperature of about 2500 degrees. The 
furnace roof and the flame under it seem to . reach temper- 
atures up to 3000 degrees or somewhat higher, the average 
being about 2800 degrees. In the firebox the temperatures 
are about the same as in the neck, 2500 degrees, Fahr. The 
latter figures are probably more accurate than those on the 
flowing metal since black body conditions are more nearly 
approached. They are if anything somewhat low. 

The following heat balance gives a general idea of fuel 
consumption in an air furnace. Since there is considerable 
variation in furnace practice the correction of heat values 
for the actual temperature of fuel and air entering the fur- 
nace was believed an unnecessary refinement. 

While based only on estimates, this balance gives a fairly 
comprehensive idea of what becomes of the heat delivered 



Air Furnace Melting 153 

Table VII 

HEAT BALANCE OF A TYPICAL AIR FURNACE 

B.t.u. per B.t.u. per 

ton ton 

charged charged 

Heat value coal burned 11,200,000 

Heat from oxidation of charge 219,400 

Heat of formation of basic silicates 30,000 



Total 11,449,400 

Latent and sensible heat of metal 878,940 

Sensible heat of flue gas 6,112,000 

Loss to incomplete combustion of C to CO only 1,232,000 

Evaporation of water in coal 10,000 

Heat value of unburned combustible in ash 37,335 

Sensible heat of slag 42,000 

Latent heat of slag (est.) 30,000 

Sensible heat of furnace structure 600,000 

Radiation conduction and unaccounted for 2,507,125 



Totals 11,449,400 11,449,400 

to the melting furnace. The values may be summarized on a 
percentage basis shown in Table. VIII. 

This indicates clearly that the larger part of the waste is 
in the sensible heat of the flue gas. This heat occasionallv 
is recovered by the use of waste heat boilers which gen- 
erate steam with the heat of the gases leaving the furnaces. 
The difficulties encountered are largely of a steam engineering 
character and arise from the intermittent supply of heat avail- 
able. 

Prof. Touceda in a paper before the American Foundry- 
men's Association in 1920, has given tentative suggestions for 
the utilization of waste heat from air furnaces. These sug- 
gestions are for various double hearth furnaces in which the 
waste heat from one hearth is used to preheat the charge in 

Table VIII 

HEAT BALANCE IN TERMS OF HEAT VALUE OF COAL FIRED 

Per cent Per cent 

Heat value of coal fired. . . 100 Heat in metal 7.81 

Heat from reactions in Heat in flue gas . . 54.70 

furnace 2.2 Heat in slag 0.64 

Incomplete combustion.. 11.30 

Heating furnace walls. . . . 5.35 

Radiation and conduction 22.40 



Total input 102.2 Total output 102.20 



154 American Malleable Cast Iron 

the other. The mechanical means are somewhat complicated 
involving movable hearths and also somewhat continuous op- 
eration. From a thermal viewpoint, however, they are most 
interesting. 

Reference has been made to the use of forced draft- in 
air furnaces. The air supply is usually at low pressure, 
about 4 ounces per square inch, although a few plants use 
pressures of a pound. In such cases the furnaces must be 
equipped with doors at the fire 'hole and skim holes. At 
least one important producer operates on natural draft alone, 
using no blowers and consequently no top blast. This partic- 
ular plant depends on extremely high stacks. Many air 
furnace stacks are from 45 to 85 feet high, and have internal 
diameters from 24 to 48 inches. The lack of agreement is 
unaccountable except on the basis of poor design. Nearly 
all air furnace stacks have capacities far beyond their actual 
requirements. 

It has been stated in the general discussion of fuels that 
both oil and pulverized coal fuel have been tried in air fur- 
nace practice. As far as the author knows, the use of oil 
never has been generally satisfactory, owing to difficulties 
in maintaining the proper furnace atmosphere, free from excess 
of air or CO 2 . 

The chemical changes in melting depend entirely upon 
the temperature and composition of gas in contact with 
the metal. The use of producer gas entailed similar diffi- 
culties and was never commercially adopted, except of course 
in open-hearth practice. Similar difficulties have been encoun- 
tered in the use of pulverized coal but have been successfully 
overcome, at least by a few combustion engineers. 

A successful equipment of this character is shown in Fig. 
80 and consists of a hopper containing the pulverized fuel pro- 
vided with screw conveyors for feeding a stream of coal 
into the current of air from the blower shown in the lower 
right hand corner of the picture. The ends of the con- 
veyor shafts are shown under the numbers 1-2-3-4-5 painted 
on the hopper. 

The current of air loaded with coal dust enters the 
furnace through three burners in the head wall of the fire 



Air Furnace Melting 



155 



box, which is blocked up; and through two burners through 
the roof at the point where the top blast usually enters. 
By proper manipulation of the relative supply of coal and 
air to these several burners, proper control may be main- 
tained and satisfactory working insured. The entire problem 




Fig. 80. A po'.vclercd coal attachment for an air furnace 

is merely the design of a burner capable of so feeding the 
fuel into the air as to maintain uniform combustion conditions 
with coal and air supply capable of regulation through a fairly 
wide range. 

Such a set of burners operated to duplicate furnace atmos- 
pheres corresponding to the best air furnace practice will 
produce results superior in control and economy to results 
under hand firing. The improvement results primarily from 
the constancy of ratio of coal to air throughout the heat, thus 



156 American Malleable Cast Iron ^ 

avoiding the losses due to alternately incomplete combustion 
and excess air w'hich occur even with the best hand firing 
when the average condition is perfectly controlled. 

. Table IX 

CHEMICAL CHANGES IN AIR FURNACE 



Metal charged 
pounds 

Fe .1901.3 
C 62.0 
Si 21.6 
Mn 11.0 
S 0.9 
P 3.2 
Clay 
O 
N 
H 
Ash 
Water 


Refrac- 
Coal Air tories 


14 

Total 


[olten metal 
Slag Flue gas 

1878.5 22.8 
49.6 ... 617.0 
15 66 


Cin- 
ders 

4.4 


6090 


671.0 
21.6 
11.0 
5.9 
3.2 
34.0 
1918.0 
7243.0 
39.0 
21.0 
14.0 




"5.6 '.'.'.'.'. '.'.'. 


5.8 5.2 
1.1 1.2 2.0 
32 


V.6 


. 34.0 
.... 1918.0 ... 
.... 7243.0 ... 
39.0 
21.0 
14.0 


34.0 
.... 15.0 1903.0 
7243.0 


2l'.0 


39.0 
'.'.','. '.'.'. ' 'l4.0 



Total. 2000.0 Ibs. 688.0 9161.0 34.0 11,883.0 1953.2 84.8 9818.0 27.0 

The author has seen the results of many tests on this 
type of equipment but it is doubtful whether data have yet 
been accumulated which warrant a definite conclusion as to 
economy of operation due to pulverized fuel. 

The tests which he has seen seem to indicate that the 
requirements as to furnace atmosphere are such that no direct 
saving on coal is practicable. The economies may rather be 
expected to result from decreased labor and refractory costs, 
and greater independence in using poor coal. 

The data at hand point also to a lower and much more 
constant loss by oxidation of the several metals than is nor- 
mal to ordinary air furnace practice, but insufficient experience 
is available to be sure whether this condition always exists. 

As a skeleton outline of the metallurgy involved in the 
operation of an air furnace the outline of the chemical changes 
shown in Table IX may be interesting. The summary is typical 
only and does not necessarily apply exactly to any given case. 

The summary is based on the weights of each material 
and each element entering into the reactions for one net ton 
of charge. 

Air furnaces usually are operated by a crew of either 
two or three men exclusive of those doing the charging. 



Air Furnace Af citing 157 

bringing in fuel and stock, etc. The majority of air fur- 
naces make a heat in 20 to 30 minutes per ton plus about 
one half hour if the furnace is hot to begin with, or plus 
one and one half hours if the furnace is cold at the start of 
the melting operations. 

Large furnaces melt faster, per ton, than small ones, 
but large heats still take longer to make. It is said that one 
plant, using oil fuel made heats around 30 tons in three and 
one half or four hours, although the writer is not prepared to 
vouch for this statement. Another plant making heats of 
this size with coal runs 16 to 18 hours to a heat, it is said. 

In most plants skimming begins when the heat is well 
melted which will be from one and one half to two hours 
before the heat is ready. In a plant where instead of skim- 
ming the slag is tapped out after the iron is poured it is 
claimed that no loss of time or fuel is incurred due to this meth- 
od. The operation is on fairly large furnaces. In spite of 
the obvious desirability of this operation, if practicable, it has 
not been adopted elsewhere. The author does not know 
whether or not this conservatism is justified. The feeling seems 
to be one of suspicion as to the general economy and practica- 
bility of the operation. 



VIII 

ELECTRIC FURNACE MELTING 

PRACTICALLY the only radical change in melting prac- 
tice which has been introduced into the malleable indus- 
try in the last half century is the use of electric furnaces. 
So far only one producer operates under this method, which is 
protected by patents covering the conditions necessary to com- 
mercial success. 

In electric operation, increased accuracy of chemical con- 
trol is made possible and the success of the melting operation 
is largely independent of variations in quality of stock and fuel 
and of blast and similar conditions. The belief that electric 
melting is adopted because it permits the manufacture of al- 
loys of compositions unattainable in the air furnace is not 
founded on fact. While it is possible, for example, to make 
iron as low as .017 per cent in sulphur, if desired, there is 
no engineering advantage in such an operation. 

Electric melting as practiced today is conducted by the 
triplex process, developed by W. G. Kranz, which, as the name 
indicates, is conducted in three distinct stages. This process 
supplements the advantages of the electric furnace with the 
use of a cupola and a bessemer converter to assist the elec- 
tric furnace in operations to which it is not so well suited. 
The rationale of the process is as follows : 

The electric furnace alone is suitable for melting or heating 
metal with slight contact with air or any other substance ex- 
cept the furnace lining and slag. Therefore, it is suited rather 
to keep the composition of its contents unaltered than to make 
changes in composition. 

Chemical changes occur therein only as a consequence of 
the addition of various alloys of slag-making ingredients and 
the effect of such additions can be quantitatively controlled. The 
changes of chemical composition easiest of attainment in the 
electric furnace are increases in silicon, manganese, or phos- 
phorus and decreases in sulphur and oxygen. Carbon can be 
added or removed, or silicon removed with greater difficulty 



160 



American Malleable Cast Iron 



but the removal of phosphorus is not practicable under the 
usual operating conditions in malleable melting. 

'Whereas the electric furnace is an expensive source of hear 
energy, the cupola is the cheapest known method for merely 




Fig. 81. Cupola producing molten iron The starting point of the 
Kranz triplex process 

melting cast iron, composition being no object. . Cupola melt- 
ing always removes at least part of the silicon and manganese 
and adds sulphur, leaving the phosphorus unaltered. The car- 
bon content is nearly independent of the mix used depending 
only on the condition of the fuel bed. The carbon content 
always is relatively high. 



Electric Furnace Melting 161 

The bessemer converter furnishes an easy and economical 
way to remove all carbon silicon and manganese from iron but 
adds a great deal of oxygen. 

The three units form an ideal team, each possessing good 
qualities to supplement the weak points of its mates. The 
cupola furnishes cheaply a supply of liquid iron of high and 
approximately constant carbon content which readily can be 
controlled as to its maximum silicon, manganese and phos- 
phorus content, but may have high sulphur from the fuel. 
Carbon, silicon and manganese can be removed from this 
metal in the bessemer converter, although oxygen may be 
added. By taking the proper relative amounts of cupola and 
bessemer metal a mixture can be produced having a 'carbon 
content close to any desired value, and which also is below 
any desired fixed values in silicon, manganese and phosphorus. 
However, it contains an indefinite and relatively large amount 
of sulphur and oxygen. 

This molten mixture can be given its final heating in the 
electric furnace without too great expense, and"*.iby the use of 
suitable slags the sulphur and oxygen can be removed without 
any -effect on the silicon, manganese, or phosphorus. Guided 
by the analysis of the molten charge, silicon and manganese 
can be added to adjust these values as desired and a product- 
made without prohibitive cost, adjusted to chemical specifica- 
tions on each of the five common elements and freed from 
oxygen. . 

These are the steps in the Kranz process, which since 
passing through the experimental stage in 1913-1914 has pro- 
duced many thousands of tons of malleable cast iron in two plants 
of the largest producer of malleable in the world. The proc- 
ess as outlined comprises melting in the cupola ; decarburizing in 
the converter; heating, desulphurizing and deoxidizing and 
raising the manganese and silicon in the electric furnace; and, if 
desired, adding sulphur in the ladle. For still greater uniform- 
ity it was once suggested that the cupola and converter metal 
be stored in a mixer prior to its introduction into the electric 
furnace, but practice has proved that this step is not nec- 
essary. 

It has been found that a product varying from dead soft 



162 



American Malleable Cast Iron 



steel to" gray iron, and including alloy steels can be made by 
this, process at the will of the operator. If dephosphorization 
is desired, for example in steel-making, an extra step is re- 
quired in the electric furnace, involving the formation of a 
dephosphorizing slag and its removal before proceeding with 
the desulphurizing and deoxidizing. 




Fig. 82. Two-ton side-blow converter producing liquid steel from 
cupola metal in triplex process 

Metallurgy of Triplex Process 

It may be well to consider the individual steps involved 
in greater metallurgical detail. In general, the melting stock 
consists of sprue and malleable scrap and high silicon pig iron. 
The mix is calculated only to be close to the desired value in 
silicon content. The manganese automatically remains low and 
with a little care the phosphorus can be kept below about 0.19 
per cent, which is all that is required. 



Electric Furnace Melting 163 

It is intended that the cupola metal shall run slightly under 
1 per cent silicon. Too low a value causes trouble from gum- 
ming' up the cupola taphole and spout and the ladle. The maxi- 
mum is determined by the metal to be made. The composition 
of the metal leaving the cupola under ordinary working condi- 
tions is approximately as follows: Carbon, 3.10; silicon, 0.80 to 
0.95; manganese, 0.12 to 0.19; sulphur, 0.09 and up, and phos- 
phorus, 0.14 to 0.19 per cent. The dimensions of the cupola 
are such as to allow the unit to run continuously to produce 
the metal required by the electric furnaces. Interruptions and 
intermissions are undesirable because they affect the tempera- 
ture of the fuel bed and consequently the carbon content. 

The ratio of iron to coke in the cupola may average 7 to 
1, varying somewhat with operating conditions. Two cupolas 
are provided and are used alternately to permit repairs. 

'i he converter easily reduces the molten metal to a composi- 
tion about as follows : Carbon, 0.20 and under ; silicon, trace ; 
manganese, trace; sulphur, 0.12 and up; and phosphorus, 0.17 
per cent and up. A considerable oxidation of iron also occurs, 
which together with the mechanical loss in the form of fine 
drops amounts to from 8 to 15 per cent of the converter charge. 
If a carbon content of say 2.60 per cent is desired, cupola and 
converter metal in the ratio of 240 to 50 will be required and the 
mixture will have a composition as follows: Carbon, 2.60; sili- 
con, 0.66 to 0.78; manganese, 0.10 to 0.16; sulphur, .095 and 
up; and phosphorus 0.14 to 0.19 per cent. 

Since each furnace heat is handled as a unit, it will be seen 
that the converter charge is dependent on the capacity of the 
electric furnace and the carbon content of the cupola metal. In 
the illustration chosen the converter must deliver 50/290 or 
about 17 per cent of the capacity of the electric for each 
blow. The metal introduced must exceed this amount by the 
expected oxidation and mechanical losses. 

The electric furnaces actually in use have a rated capacity 
of six and 15 tons, respectively so that when working at capac- 
ity the converter would have to deliver 1.02 and 2.35 tons 
respectively. 

The electric furnaces used are of the Heroult type, operat- 
ing on 3-phase, alternating current. The 6-ton units consume 



164 American Malleable Cast Iron 

800 kilovolt-amperes of power at 80 to 100 volts and the 15 -ton 
units from 18,000 to 22,000 kilovolt-amperes at from 90 to 
110 volts. 

Handling Charge in Furnace 

The internal diameter of the larger units is approximately 
10 feet. In all cases the bottoms are dolomite and the lining 
of the side walls magnesite. The molten metal is introduced 
into the furnace, the arc formed, and a lime slag made on the 
surface. The slag-making ingredients are lime, fluorspar and 
coke; in amounts determined by the working conditions and not 
by weight. About 150 pounds of lime and coke and 100 pounds 
of fluorspar may be used in a 12-ton heat, the active ingredient 
of the resulting* slag being calcium carbide, CaC 2 . The ac- 
tual amounts of slag-making ingredients are however not de- 
termined by weight but by the appearance of the slag and 
the "operating conditions of the furnace. This carbide reacts 
energetically with any metallic oxides present. For instance 

3 FeO + CaC 2 = GaO -f 3 Fe + 2 CO 

No appreciable amounts of CaC 2 are formed until the oxy- 
gen is practically completely eliminated. At that stage the 
elimination of sulphur begins, the products being CaS and 
carbon, which dissolves in the metal. This process can not 
be conducted under any but a reducing condition for CaS 
is easily oxidized to CaO, the sulphur unfortunately not burn- 
ing to SO 2 but dissolving in the iron. This introduces certain 
difficulties in lowering the silicon content. For example silicon 
is easily and almost quantitatively oxidized by ore, the reaction 
presumably being 

Si + 2 Fe a O 3 = SiO 2 + 4 FeO 

Unfortunately the FeO of the resulting slag immediate- 
ly reacts as follows : 

FeO + CaS = FeS + CaO 

and the desulphurizing must be recommenced. The removal 
of silicon can be conducted in this way, but it is a cause 
of difficulty in the maintenance of the desired slag. 

Fortunately the high carbon alloys occurring in malle- 
able practice do not take up carbon from the carbide slags 
used to any appreciable extent, nor does the CaC 2 reduce a 



Electric Furnace Melting 165 

considerable amount of silicon from any calcium silicates which 
may be present. 

A sample is taken for analysis after the metal is thor- 
oughly mixed in the furnace and should show a correct 
amount of carbon and phosphorus, and a deficiency in sili- 
con and manganese. These latter two elements are added as 
ferrosilicon, ferromanganese, Spiegel or similar alloys. Carbon 
can be added as pig, cupola iron, or in very 'hot heats as coke 
or can be reduced by steel additions. Silicon can be removed 
with ore as previously described but it is not intended that this 




Fig. 83. Transfer train consisting of electric motor car and trailer 

with crane ladle. This equipment is used in carrying cupola 

and converter metal to the electric furnaces 

be done in regular practice. The removal of phospohrus from 
malleable heats is so expensive that it is cheaper to scrap such 
heats than to attempt to correct them. 

Temperature Limited by Operations 

The temperature to which electric metal can be heated 
depends only on the refractories used and in commercial prac- 
tice is from 2600 to 3000 degrees Fahr. The figures are by 
radiation pyrometer and in the writer's judgment are likely 
to be lower than the correct values. More recent data by optical 
pyrometer show temperatures from 2900 degrees to 3000 de- 
grees Fahr. It appears therefore that the figures around 2600 



166 American Malleable Cast Iron 

degrees arose from an improper correction for coefficient of ra- 
diation. The relative merits of the two systems of pyrometry 
have been discussed in connection with air furnace melting. It is 
customary to take a heat away in one or two large ladles and to 
proceed immediately with another heat. The advantages of the 
process already have been pointed out and all point back to ac- 
curacy of control. The most serious limitation is the expensive 
first cost of the melting installation, which places it beyond the 
reach of the small producer. Furthermore the process is not 
suited to intermittent operation involving the banking of cupolas 
and filling of electric furnaces with coke. To obtain success- 
ful results a 24-hour day during the working week is neces- 
sary. Counting iy 2 hours per heat or 16 heats per day and 
allowing for some loss of time for repairs between heats, and 
bearing in mind possible reductions in economy where very 
small units are used, a simple calculation will indicate that suc- 
cessful operation can be had only in plants of fair capacity. 

The two plants now in operation are equipped with three 
small and two large furnaces, respectively, and are intended 
to operate on large tonnages. Furthermore, the crane service 
required for the handling of hot metal, etc., almost precludes the 
introduction of hot melting into any but an especially built plant, 
thus further limiting its general introduction. 

All this is in addition to the limitations to the general use 
of the process due to its control through patent protection. Fur- 
nace repairs are relatively much less frequent in electric fur- 
naces than in air furnaces. The bottom is taken care of after 
each heat. The magnesia side walls and silica roof each last 
from 120 to 240 heats, while the basic bottom, being repaired 
after each heat, lasts indefinitely. 

The cost of heat in the electric furnace is high, but on the 
other hand the utilization of heat reaches an extremely high 
efficiency owing to the elimination of the losses in fuel-fired 
furnaces arising from the escape of the hot products of com- 
bustion. The current is on about one hour for each heat. 

Charging, tapping and patching consume up to 45 min- 
utes of time. Cupolas are intended to run a week on each 
lining but usually are repaired at 24 to 72-hour intervals. 



Electric Furnace Melting 167 

The converters are of the side-blown type of a capacity 
suited to the Heroult furnace they serve and are lined with 
ganister. Converter bottoms last about a week, and the tops 
nearly indefinitely. 

It will be instructive to follow quantitatively the chemical 
changes occurring. The following analysis is typical of the 
slag produced by the cupola. 

Per cent 

SiO, -52.90 

A1,O, 12.80 

FeO 5.10 

Fe a O 00 

MnO 2.60 

CaO 21.30 

MgO 3.70 

S 0.20 

Undetermined and .error 1.40 

100.00 

This is practically a mixture of molten refractory and 
limestone, little oxidation of the metal having occurred under 
the strongly reducing conditions of the cupola. 

Assuming that the cupola charge consists of 10 per cent 
silicon pig, sprue and malleable scrap, the two latter averaging 
0.70 silicon, in order to have a mixture at 1.10 silicon the mix 
will contain 4.3 per cent pig iron and, for example, 40 per 
cent sprue and 55.7 per cent malleable scrap. The average 
analysis of such a mixture figures out carbon, 2.68; 
silicon, 1.10; manganese, 0.27; sulphur, 055 and 
phosphorus, 0.177 per cent. This metal, when melted 
and leaving the cupola has a composition of carbon, 3.10; sili- 
con, 0.85; manganese, 0.15; sulphur, 0.09 and phosphorus, 0.177 
per cent. This change of composition coupled with the pre- 
viously given slag analysis amounts to a net loss by oxidation 
of 0.166 per cent of the total weight charged. 

The oxidation of silicon, manganese and iron is nearly 
balanced by the gain in sulphur and carbon from the fuel. In 
practice there is a loss of noticeable magnitude due to me- 
chanical causes. By calculation the slag corresponds to 5.8 per 
cent of the weight of the charge; 1684 per cent is derived 
from oxidation of the metal ; 25 per cent from the lime- 
stone added as a flux ; and the balance from the fusion of the 



168 



American Malleable Cast Iron 



furnace lining, coke ash, impurities in stone, etc. Assuming 
the limestone to have been 90 per cent CaCO 3 , the weight of the 
limestone added was about 50 per cent of the slag weight or 
2.9 per cent of the weight of metal charged. The limestone 
lost to the flue gas an amount of CO 2 equal to 11 per cent of 
the slag weight. 

When the cupola metal is blown in the converter it be- 




Fig. 84. Heroult electric furnace in which cupola and converter 
metal is charged for final step in triplex process 

comes a steel containing, for example: Carbon, 0.10; sulphur, 
0.095; and phosphorus, 0.187 per cent. The slag formed has a 
composition of which the following is typical : 

Per cent 

SiO 3 57.50 

A1 2 O 3 1.43 

FeO 34.41 

Fe,O, 1.45 

M-nO 3.80 

OaiO 0.25 

M-gO 0.34 

Error and undetermined 0.82 



100.00 



Electric Furnace Melting 169 

A loss in weight of 5.36 per cent of the weight charged 
into the converter is indicated. In practice a larger loss is 
noted due to mechanical losses and to considerable amounts 
of iron oxide which escape as fume and are not taken into ac- 
count in the analysis. 

The slag is equivalent in weight to 4.86 per cent of the 
metal charged. Of this slag 50.08 per cent is an oxidation prod- 
uct of the metal and 49.92 per cent is fused refractory. 

In the electric furnace no oxidation takes place, the only 
elements affected being sulphur and oxygen which leave the 
metal to become calcium sulphide and carbon monoxide, respec- 
tively. The former remains in the slag, while the latter escapes 
as a gas. Therefore the slag in the electric furnace is not in 
any material degree derived from the elements in the iron, but 
depends for its quantity and largely for its composition on the 
slag forming additions used. These are lime (CaO) fluor- 
spar (CaF 2 ) and coke. The supposition is that the coke and 
lime form .calcium carbide which removes both sulphur and 
carbon. 

However the slags never are nearly pure mixtures of CaC 2 
and CaF 2 . Typical slag obtained under conditions which would 
possibly have destroyed "any CaC 2 by the action of the atmos- 
pheric moisture had a composition as follows : 

Per cent 

SiO, 29.80 

A1,O 3 2.85 

FeO 0.50 

Fe 2 O 3 nil 

M.nO 0.18 

CaF 2 0.70 

CaO 44.51 

MigO 7.55 

CaiS 7.20 

Undetermined '6.71 

100.00 

From the behavior of the slag it seems reasonable that 
most of the lime is combined with silica and that there is but 
little free CaO as Ca(OH) 2 either normally present or derived 
from the decomposition of carbides. Possibly the CaO from 
these sources may run to 5 per cent or similar undetermined 
amounts. 



170 



American Malleable Cast Iron 



Possibly the MnO s'hown is MnS floating up from the met- 
al, in which case the CaS would be reduced and CaO increased 
to allow for the S combined with Mn. The fluorine apparently 
is largely eliminated in the furnace. Data as to slag quan- 
tities are uninteresting as having no connection with the metal- 
lurgical principles. The additions may amount in the aggre- 
gate to perhaps 1 or 1.5 per cent of the weight of the metal. 




Fig. 85. Heroult furnace tilted for pouring 

Metallurgy of the Slag 

Assuming a desulphurization of .07 per cent, the slag 
composition referred to and excluding sulphur from the coke 
amounts to around 44 pounds of slag per ton of metal. Of 
the slag the SiO 2 A1 2 O 3 and MgO are primarily derived from 
the furnace lining. Those comprise 40.2 per cent of the en- 
tire slag. Therefore for each ton of metal 17.6 pounds of re- 
fractory are melted and 26.4 pounds of slag is formed from 
lime, fluorspar and carbon and from the metal itself. Of the 
ingredients from the metal the principal item in weight is 1.4 



Electric Furnace Melting 171 

Table X 

BALANCE SHEET FOR DISTRIBUTION OF METALLOIDS IN ELECTRIC FURNACE 

PRACTICE 

In pounds per ton of cupola charge 
From From 

In cupola cupola converter 

charge coke air Total 

C . 53.6 8.3 61 



Si 22.0 

Mn 5.4 

P 3.54 

S 1.10 0.7 

O ... .. 0.60* * 0.60 

Fe 1914.36 1914.36 



22.0 
5.4 
.3.54 
1.80 



In electric To electric 

In final In cupola In con- In con- furnace furnace 
product slag verter slag verter gas slag atmosphere 

C 51.90 ... ..Q> 10.0 0.00* 

Si 14.17 5.0 2.83 '. . . 0.00* 

Mn 2.46 2.4 0.50 . . . 0.04 

P 3.54 ... ... ... 0.00* 

S 0.08 ... ... ... 1.00 

O ...* ...* ...* ...* 0.60 

Fe 1904.84 4.8 4.60 ... 0.12 

*Includes only those amounts at some stage alloyed with the 
molten metal. 

pounds of sulphur, the MnO and FeO being only about 0.3 
pounds per ton. Deducting these two, the slag has 24.7 
pounds of material per ton of metal derived from 
the slag-forming additions. All of these figures men- 
tioned are to be considered as suggestive only. A 
balance sheet of the elements concerned in the triplex process is 
shown in Table X. It must be understood, however, that the 
process has not been quantitatively investigated to the point 
where all the reactions are clearly worked out. The figures in 
the balance sheet for oxygen are merely estimates. The sulphur 
data are not based on a complete series of tests, but are in 
accord with current practice. The table neglects oxygen in ori- 
ginal metal and final product. Ferromanganese and ferrosilicon 
are not supposed to be added. If charged into the electric, 
these alloy quantitatively with the charge. 

Heat Balance of Triplex Process 

A heat balance for the triplex process is extremely inter- 
esting as giving an insight into the character of heat losses re- 



172 



American Malleable Cast Iron 



Table XI 

GENERAL HEAT BALANCE OF TRIPLEX PROCESS 
Cupola 

B.t.u. B.t.u. 

Heat value fuel 3,718,000 

Total heat, metal 1,692,000 

Sensible heat, slag 63,800 

Sensible heat, flue gas 180,000 

Heat value of Fe, CO in flue gas 744,000 

Radiation and unaccounted for 1,038,200 

Total output 3,718,000 

Converter 

Total heat of metal charged 282,000 

Heat of combustion of C, Si, Mn 93,400 

Total input 375,400 

Total heat, metal 292,800 

Sensible heat, slag , 10,900 

Sensible heat, gas and undetermined 71,700 

Total output 375,400 

Electric Furnace 

Total heat metal charged 1,690,800 

Heat equivalent of electric input 564,200 

Total input 2,255,000 

Total heat, metal 1,865,000 

Sensible heat, slag 23,000 

Radiation and undetermined 367,000 

Total output 2,255,000 

maining. Unfortunately the results of complete tests of the 
process including all the factors involved are not available. Also 
the heat of formation of some of the compounds entering into 
the reaction, more particularly in the electric furnace are not 
known. In the absence of this information the following bal- 
ance has been built up on estimates from other sources of the 
composition of gas leaving the cupola and converter, and of 
the temperature of the cupola gas, and of the metal at various 
stages. Also the heat of formation of the slag has not been 
considered a source of energy nor has allowance been made 
for the latent heat of fusion of slags and refractories. 

The presence of oxygen in the metal, at various stages has 
not been followed quantitatively so. that no account of the 
thermal effect of the formation and reduction of FeO can be 
taken. The latter items are included among the undetermined 



Electric Furnace Melting 173 

Table XII 

HEAT BALANCE OF UNITS IN TRIPLEX PROCESS 

B.t.u. B.t.u. 

Heat value of coke 3,718,000 

Heat value of current 564,200 

Heat combination of Fe Si, Mn and C 93,400 



Total heat input 4,375,600 

Incomplete combustion in cupola. . . . . x 744,000 

Sensible heat, slag : 63,800 

Sensible heat, flue gas 180,000 

Radiation and undetermined 1,038,200 



Total cupola loss 2,026,000 

Sensible heat, converter slag. 10,900 

Sensible heat, gas and undetermined 71,700 



Total converter loss 82,600 

Ladle loss by radiation (preheated ladle) 12,000 

Sensible heat, slag 23,000 

Radiation and undetermined 367,000 



402,000 
Total heat, metal 1,865,000 



Total output 4,375,600 

losses at the various stages of the process. However, the 
balance in Table XI, based on one ton of metal charged into 
the cupola and on temperatures above atmospheric may be 
regarded as indicative of the major items. 

The cupola utilizes 45.5 per cent of the heat of the fuel. 
The converter delivers 77.7 per cent of the total heat sup-, 
plied, using 11.5 per cent of the heat of combus- 
tion of the 'elements burned in further heating the 
metal. The ladle loss in transferring the metal, not 
shown above, amounts to less than 1 per cent. The electric 
furnace delivers in the metal 82.7 per cent of all the heat 
furnished it, using 30.9 per cent of the thermal equivalent of 
the electric input in heating the metal. 

Heat Balance in Per -Cent 

A summary of the heat balance based on the process as a 
whole appears in Table XII. The tabulation may be condensed 



174 American Malleable Cast Iron 

somewhat further and expressed in percentages of the total 
heat supplied by fuel and power as follows : 

Per cent 

Heat of combustion fuel 86.5 

Heat equivalent of power 13.5 

Heat of combustion of elements in converter 2.2 

Heat loss in cupola 47.3 

Heat loss in converter 1.9 

Heat loss in ladle 0.3 

Heat loss in electric furnace 9.1 

Total heat metal 43.6 



Totals 102.2 102.2 

The figures show the relatively very great thermal effi- 
ciency of the process as compared with air furnace or open- 
hearth melting. A heat made from cold stock in the electric 
furnace would show a still hig'her thermal efficiency, approxi- 
mating that of the electric furnace alone. This would not, how- 
ever, correspond to a greater economic efficiency in view of the 
greater cost of a 'heat unit as electric energy than as coke. 

From the viewpoint of fuel consumption a vast consideration 
of the electric, furnace is not complete without pointing out that a 
consumption of 21/2 pounds of coal per kilowatt-hour is an ex- 
tremely economical figure, attainable only in unusually large 
turbine-driven plants. 

There would be superimposed on this further transformer 
and line' losses so that the electric furnace may get from 4 
per cent to 8 per cent of the energy of the boiler fuel as 
electric energy. 

This consideration, coupled with the high overhead for the 
powder plant, accounts for the great cost of heat energy derived 
from electric power as compared with that of an equal amount 
of heat energy potentially present in the fuel. 



IX 

CUPOLA AND OPEN-HEARTH MELTING 

IX ADDITION to air and electric furnace melting, which 
was discussed in Chapters VII and VIII, there are two com- 
mercial methods of melting malleable. That which employs 
the cupola can he dismissed with a few words, since its use for 
producing specification metal has been prohibited by the specifica- 
tions of the American Society for Testing Materials since their 
first revision. 

The objections to cupola metal are based on lack of uni- 
formity of product and lack of control. Because of construc- 
tion of the cupola and its method of operation, no large amount 
of liquid iron is accumulated at one time; therefore there is no 
assurance that successive taps will be even nearly the same in 
composition unless the charge consists of only one material, 
which manifestly is impracticable. 

These variations are of no consequence in the general run 
of gray iron castings, but in malleable practice with its much 
reduced practicable range of composition they are prohibitive, 
especially for large work.'- Furthermore, since the cupola runs 
continuously for several hours there is no means of judging the fit- 
ness of the iron for its intended purpose either by analysis or 
fracture before it is poured. 

Control of Metal Limited 

Even when the best possible uniformity is secured the cu- 
pola process has limitations of control which render it unsuitable 
in the production of a general run of malleable castings. The 
molten iron runs down through a mass of' incandescent coke, 
meeting in the spaces between the coke a stream of gas, 
originally air, but converted by the fuel into a mixture of car- 
bon dioxide, carbon monoxide and nitrogen. 

Under any given operating condition, especially as to tem- 
perature, a definite equilibrium exists which determines the com- 
position of the products of combustion in contact with mean- 



176 



American Malleable Cast 




bo 



Cupola and Open Hearth Melting 177 

descent carbon at that temperature. The descending liquid iron 
thus passes into a zone in which temperature and gas composi- 
tion are adapted to equilibrium with molten iron of only one 
specific carbon content and capable of adding or removing car- 
bon easily if the metal comes down lower or higher than this 
value in equilibrium with the gas phase. Therefore a cupola 
produces metal of a carbon content almost independent of that 
of the charge and dependent solely on the combustion conditions. 
The possible range of working conditions is such as to 
produce metal containing from about 2.70 to 3.25 per cent carbon 
a value too high for the production of a high class product 
except in small work. The sulphur content of cupola metal also 
is invariably high in view of the intimate contact of molten 
metal and fuel. 

Some cupola metal made for extremely small work thus is 
converted into white heart malleable, possibly without the full 
understanding of the operator, and the work is annealed by de- 
carbonization of the thin sections and not by graphitization. 

The surviving successful application of the cupola process 
to black heart malleable is in the manufacture of pipe fittings 
where the product usually does not have the greatest possible 
strength. 

The metallurgy of cupola melting has been considered in Chap- 
ter VII in connection with the triplex process. However, a 
higher fuel ratio is common in ordinary cupola melting than in 
the triplex process because the iron must leave the cupola at a 
higher temperature in order to run into molds than if it is to be, 
handled only by a crane ladle. 

A ratio of metal to fuel of between 4 to 1 and 6 to 1 may 
represent operating practice, and this represents the one great 
advantage of the cupola cheapness both of construction and 
operation, the utilization of heat being about two or two 'and 
one-half times as efficient as in the air furnace. 

Open-hearth melting, especially when large tonnages and 
continuous operation are involved, should be a desirable method 
of operation. That its practice is confined to relatively few 



178 



American Malleable Cast Iron 




o 
O 

'o 

o 
c7) 
U) 

'5; 
v- 

U 

oo 
fcio 



Cupola and Open Hearth Melting 179 

plants may be due to the conservatism of the industry and to 
the tonnage limitation. 

In general, the open-hearth furnaces used in the malleable" 
industry are similar in construction to those used in steel making 
and in size represent the lower limits of capacity used* in that 
industry. Some experimental heats have been made in basic 
furnaces but acid-lined furnaces apparently are used for com- 
mercial operation. 

The melting operation is similar in principle to aar furnace 
melting, except in the application of the heat. 

Furnaces ranging in capacity from 5 to 20 tons have been 
used, the larger units being preferred when practicable. The 
furnace roofs are of silica brick and the bottoms of silica sand. 
The regenerative system upon which the operation depends is 
so well known as hardly to require description. The products of 
combustion leaving the hearth pass through checkers of fire 
brick and impart their heat to these brick. When the brick is 
thoroughly heated the direction of gas passage is reversed, the 
air being drawn into the furnace through the previously heated 
checkers. The products of combustion pass out through check- 
ers at the opposite end of the furnace. When producer gas 
is used it also is preheated. The incoming air gradually cools 
the hot set of checker work while the products of combustion 
heat the checker at the outlet end when the latter grow hot the 
direction of passage is again reversed, this operation being 
continued. 

Using Heat of Flue Gases 

The period of reversal depends upon the heat capacity of 
the checker work and in ordinary design a reversal every 15 to 
30 minutes may be contemplated. The object is to utilize the 
sensible heat of the flue gases. The gases leaving the iron can- 
not impart heat thereto unless their temperature is above that of 
the metal. However, their heat can be imparted to the furnace 
content by using it to preheat the air and sometimes the fuel 
used before the combustion begins. In this way a higher furnace 
temperature and lower heat loss are maintained. 

The heat loss depends upon the temperature of the out- 



ISO 



American Malleable Cast Iron 




f^&TSfa^W^ffifflfliXfff'. 



Cupola and Open Hearth Melting 



181 




flfrf 

4) C <* O M 



^ !3 



cj jn< 
rt = 
G H 



jc -^ rt o ^ 0-5 



S - ^Ilil 1 

s SS'sIl s 



- S 



-a Z X 



182 American Malleable Cast Iron 

going gases and this in turn upon the volume of the regenerator 
chambers and the period of reversals. In theory the outgoing 
temperature might be reduced to that of the incoming air and 
gas but this is practically impossible. 

Campbell states that open-hearth steel furnaces should be 
capable of operation without the stack gases attaining a red heat. 
However, this result is not often attained. Assuming this red 
heat to be 900 degrees and the gas composition to be the same 
as in air furnace melting the sensible heat of the out-going gases 
is only 9/25 of that of the air furnace, counting from degree 
Fahr. as a basis (which is not strictly correct). Therefore the 
heat value saved in the regenerators is 17/25 of that lost in 
the stack in air furnace practice. Using the heat loss in sensible 
heat of gases, leaving the air furnace as 7800 B.t.u. per pound 
of coal, and counting again from degrees Fahr., the heat saved 
per pound of coal would be 5304 B.t.u. or over one-third the 
heat value of the fuel. 

Quoting Campbell in Manufacture and Properties of Struc- 
tural Steel> for a given sized chamber the escaping gases are 
a certain number of degrees hotter than the gases that go into it. 
If this difference is 300 degrees, then if the entering gas is 400 
degrees, the escaping gases will be 700 degrees, and if the en- 
tering gases are 700 degrees the outgoing gases will be 1000 
degrees. It will be seen that this reasoning implies that no 
change of economy results from changes of temperature in pro- 
ducer gas passing from the producer to the furnace. If 
no heat is lost in the gas while passing from the producer to 
the regenerator a loss corresponding to this saving is incurred 
in the outlet gases. 

Since open-hearth furnaces are much less common in the 
malleable industry than air furnaces, correspondingly less is 
known of their design and operation. For general information 
on open-hearth operation the interested reader is referred to 
the literature of the subject regarding steel melting. 

By kindness of Messrs. Lanihan and Fulton; the writer has 
been given access to a certain amount of data accumulated in 
the successful operation of open-hearth furnaces by the Fort 



Cupola and Open Hearth Melting 183 

Pitt Malleable Iron Co., Pittsburgh. Much of what follows is 
based on that practice supplemented where necessary by con- 
clusions drawn from other sources. 

Malleable melting in the open hearth differs metallurgically 
in one essential respect from steel melting. The steel maker 
operates to greatly reduce the carbon and silicon content of the 
bath by oxidation. In malleable practice this oxidation must 
be kept down as much as practicable to insure control and re- 
duce melting losses. Therefore the furnace atmosphere is sub- 
ject to the same limitations as to composition as in air furnace 
practice. In view of the fact that this oxidation is actually kept 
down to about the same limits as in air furnace practice it seems 
reasonable in the absence of direct figures to assume that the CO, 
CO 2 , O and N in the products iof combustion should be about 
the same as is given in Chapter VI. An essential difference, 
however, will be the presence of a greater proportion of steam 
or water, since these furnaces are operated on natural gas and 
oil. 

In the chapter on air furnace melting, the flue gas analysis 
was given as oxygen, 1.1; carbon dioxide, 12.7; carbon mon- 
oxide, 3.6; and nitrogen, 82.6 per cent. Assuming the gas in 
the present case to have this composition and assuming that the 
formula of the petroleum is C n H 2n + 2 the ratio of C to H 
in the fuel will vary from 3 to 1 to 6 to 1, depending on the 
molecular weight of the hydrocarbon being burned. We can 
calculate the flue gas per pounds of fuel closely. 

Assuming a ratio of C to H of 5 3/4 (which probably is a 
little high but will compensate for the inaccuracy introduced 
by neglecting the carbon burned from the metal) we may con- 
clude that one pound of fuel will require nearly 17.1 pounds of air 
for combustion, yielding 18.1 pounds of gas made up of the 
following amounts of the several constituents: 

Pounds 

<? .152 

0, 2.430 

CO 435 

H 2 o .'..'.'.':::::::::: 1:322 

N 13.76 



184 American Malleable Cast Iron 

If a gas analysis were ma.de, the water would not be found, 
being condensed to a liquid in sampling for analysis. The com- 
position by volume apparently would be : 

Per cent 

O 0.8 

CO, 9.7 

CO 2.8 

N , ..86.7 



Total 100.0 

In the absence of actual analyses this may be taken as 
representing a near approach to the combustion conditions to be 
expected using oil fuel. The differences using gas fuel are 
probably insignificant as compared with the probable inac- 
curacies in some of the assumptions made. 

The chemical changes occurring in the bath are identical in 
character and similar in magnitude to those occurring in the air 
furnace. 

The oxidation losses in open-hearth melting have been in- 
vestigated, in the light of the changes of composition during the 
process as determined at the Fort Pitt foundry. Typical re- 
sults are given both in per cent of the original charge and in per 
cent of the original amount of the element present : 

Loss in Open-Hearth Melting 

Total charge Amount of element 

100 per cent 

16.9 

22.9 

40.5 

0.0 

10.00 
1.6 

Total 2.51 

It will be noted that the oxidizing conditions are similar to 
those encountered in air furnace practice and described under 
that heading. The gain in sulphur and loss of carbon, silicon 
and manganese are less in open-hearth practice than in air fur- 
nace practice. However the oxidation of iron is sufficiently 
greater to keep the net loss at nearly the same figure as in air 
furnaces. 



c 


100 per cent 
... 49 


Si 
Mn 


0.29 
154 


P 

s 


0.00 
004 


Fc . 


. 1.58 



Cupola and Open Hearth Melting 185 

* 

These conditions can be further followed by a consideration 
of the composition of open-hearth slag. A representative sample 
of this material had the following analysis : 

Per cent 

FeO 37.6 

Fe,0 3 2.7 

MnO 3.87 

SiO, 51.30 

Al,,6 3 1.95 

Undetermined 2.58 



100.00 

The greater oxidation of iron as compared with manganese 
is evident. The decrease in A1 2 O 3 also is apparent, since the 
refractory lining is largely silica instead of largely alumina as 
in fire brick structures. The silicon entering, the slag from the 
metal corresponds to 12.1 per cent of the weight of the slag. 
Therefore, the slag consists of 56.27 per cent compounds de- 
rived from the oxidation of the charge and 43.73 per cent melted 
refractories. 

Comparing the iron content of the slag with the iron oxi- 
dized we find that apparently about 101 pounds of slag, or 
5.05 per cent of the weight of the metal are formed per ton 
charged and hence by calculation 44 pounds of refractories or 
2.2 per cent are melted per ton of metal charged. These figures 
again are similar in order of magnitude to those determined by 
more exhaustive study on air furnaces. 

Heat Balance Based on Assumed Data 

The heat balance of an open hearth can be calculated 
readily from a knowledge of the reactions occurring. Unfortu- 
nately we have not a complete record of tests involving all the 
factors to be considered. From the preceding assumptions and 
the fact that the average natural gas consumption of the furnace 
in question was about 8200 cubic feet per ton when regularly 
operated, the balance in Table XIII may be considered as an ap- 
proximation, no claim to precision being warranted by the char- 
acter of the data. 

Expressing results in per cent of the heat value of fuel 



186 



American Malleable Cast Iron 



used and summarizing a little further the data may be expressed 
as in the summary in Table XIII. 

In comparison with air furnace practice it will be noted 
that a general increase in economy is shown, 10.22 per cent 
of the heat of the fuel being effective instead of 7.81 per cent. 
The waste in sensible heat of flue gas and the loss due to in- 
Table XIII 
HEAT BALANCE OF OPEN-HEARTH FURNACE 

B.t.u. B.t.u. 

Heat value of fuel 8,514,000 

Heat value of metal oxidized 294,000 

Heat formation of silicates (estimated) 36,000 

Total heat input , 8,844,000 

Latent heat of fusion and sensible heat of metal 879,000 

Sensible heat of flue gas t 3.007,000 

Loss due to uncomplete combustion of C to CO only.... 545,000 

Sensible heat slag 51,000 

Latent heat fusion slag estimated 36,000 

Radiation conduction and stand by losses 4,326,000 

Total heat output 8,844,000 

Summary of Pleat Balance of Open-Hearth Furnace 

.Per Pei- 
cent cent 

Heat value of fuel 100.00 

Heat reactions in bath 3.86 

Totals 103.86 

Heat in metal 10.22 

Heat in flue gas 35.33 

Heat in slag 1.02 

Incomplete combustion , 6.41 

Radiation and standby losses 50.88 



103.86 

complete combustion are decreased because, being gaseous or 
liquid, the fuel is all consumed and because hydrogen is present. 
Since the furnace constantly is kept hot, there is no perceptible 
heat loss due to sensible heat of furnace wall. However, 
there is a large loss due to the need of keeping some heat on the 
furnace during, idle periods. 

This loss, increasing with the idle time, makes 24-hour 
a day operation highly desirable. With such operation it seems 
that possibly 25 per cent of the present fuel could be saved. 
Radiation and conduction losses would still exist but stand bv 



Cupola and Open Hearth Melting 187 

and sensible heat losses would be eliminated. Under such 
conditions an economy of about 14 per cent in the use of fuel 
might be reached as against about 8 per cent in air furnace 
practice in 24 hour operation. 

Open-hearth furnace heats range in size from 14 to 20 
tons or more, preferably at- least two heats a day being made on 
a furnace. Fuel in the plant in question is natural gas or 
oil. The gas consumption varies from 8200 to 9100 cubic feet 
per ton. 

Oil fuel runs from 43 to 62 gallons per ton. In both cases 
the results depend on whether or not the furnace operates con- 
tinuously or intermittently and on the condition of the furnace. 

For heats from 15 to 18 tons in size about 5 to S T / 2 hours 
are consumed in melting; 20-ton heats take around six hours. 

The efficiency of design is largely dependent on the checker 
arrangement' with its corresponding effect on the utilization of 
waste heat. Unlike an air furnace, the open hearth requires 
rather infrequent but very extensive repairs. Furnace bottoms 
and banks are of course continuously watched and patched be- 
tween heats. One furnace operated two years and two months, 
making 1282 heats with no repairs except cleaning the checkers 
and changing doors. The same furnace has since made 2051 
heats with one cleaning of the checkers, a new roof, front, back 
and bridgewalls, an unusual record. 

On the other hand, another furnace, running on one heat 
a day and frequently cooled ran only 200 heats before extensive 
repairs were required, showing the extreme destruction from 
unequal expansion in heating and cooling of the brick. 

The labor to operate an open hearth consists of either three 
or two and one half men per furnace. Charging is not included 
in this labor. The 'work of charging into a furnace through 
doors is prohibitively heavy and charging machines are almost 
a necessity. 

No data as to the use of pulverized coal or producer gas 
are available for malleable melting, although both of these fuels 
are -used in steelmaking with great success. 



X 

ANNEALING PRACTICE 

THUS far in the discussion of malleable foundry practice 
the various methods of producing molten white cast iron 
have been considered. The next step is converting the 
hard iron casting into the malleable casting of commerce. 

Unfortunately this process still is most widely known as 
annealing instead of the better terms, heat treating, graphi- 
tizing, or converting. It is the intention to describe mainly 
the practical execution of the process in this chapter. 

The process primarily is only an effect of time and tem- 
perature, and not a chemical one in the sense of a change 
of composition. Therefore a general consideration of the 
subject should begin with the viewpoint of the general meth- 
ods of application of temperature to the product, leaving for 
later discussion the practical limitations of temperature and 
time and the incidental change of chemical composition in- 
volved. 

The practice of annealing as originally developed con- 
templated packing the castings in a chemically active pack- 
ing material in cast iron containers and transferring them 
into an oven where the desired heat treatment was executed. 
This method of operation still is used conveniently, although 
it is now thoroughly recognized that the use of packing is 
by no means an essential in the process. In addition to its 
control over the chemical changes occurring in the product 
by oxidation, the packing has the important function of sup- 
porting the casting while hot. 

Packing Supports Castings 

Commercial annealing contemplates the attainment of 
maximum temperatures of from 1500 to 1850 degrees Fahr. 
and the maintenance of such temperatures for days at a time. 
Obviously iron at this temperature will be fairly soft and a 



190 



American Malleable Cast Iron 



casting of any intricacy would be irretrievably ruined by 
sagging if not supported. Except in such special cases as 
may arise w'here the design of the part is such as to be prac- 
tically self supporting, some method therefore must be 
adopted for preventing the distortion of the casting either 
under its own weight or under the weight of the castings in 
the pots above it. 

A second function of packing, in its present application 
is to hinder rather than to accelerate oxidation. If a casting 



r 





Fig. 89. Separator plate designed to eliminate 
with annealing pots 



use of packing 



be exposed directly to the products of combustion of the fuel 
at these high temperatures it will come out badly scaled and 
possibly ruined for the purpose intended. There are few 
better means of protecting the casting from furnace gases 
than enclosing it in a fine inert packing. 

How Castings Are Packed 

The process of packing is carried out in malleable an- 
nealing as follows. First a bottom which is practically a 
heavy cast iron bench with legs 4 or 6 inches high is set on 
the floor. On this is set a pot which is an approximately 
rectangular or round frame, usually about 12 inches deep. 



Annealing Practice 191 



The size and form of pot depends largely on the work 
handled and to some extent on the whim .of the annealer. 

Unusually large pots fill the space in the furnace more 
completely than smaller pots but heat slowly and rather un- 
evenly due to the low conductivity of the packing 'material. 
Round pots do not distort as much due to the sagging of 
the contents as do those with flat sides. However, they heat 
more slowly and do not utilize the furnace capacity as ef- 
ficiently as the latter. Furthermore in most places the pots 
are handled by hand so that too great weight must be 
avoided. The pots must be about 1 inch thick to have a 
commercial life and hence extremely large pots can not be 
made as deep as smaller ones. Also when large they are not 
easily stacked very high and therefore a waste of oven ca- 
pacity may result. 

The writer has seen rectangular pots as large as 30 x 36- 
inches inside used where the character of the castings made 
this size unavoidable. Round pots frequently are 24 to 30 
inches inside diameter. Rectangular pots running from 
about 14 x 18 inches to 16 x 24 inches inside are common. 

AY here the work is of such character as to stack solidly 
together, a pot of the smaller size or only a little larger will 
give a stack as heavy as can be readily moved or uniformly 
heated. In thin, sprawly work larger sizes may be unavoid- 
able. The pots are made of white cast iron either like that 
in the castings or of a cheap cupola iron high in sulphur 
and low in manganese which will not graphitize. 

Method of Packing Pots 

After the pot has been placed upon the stool, the first 
step is to put in a layer of packing from one to three inches 
thick. On this are shoveled or packed sufficient castings to 
nearly fill the pot. Small castings, for example link belt 
parts, are shoveled in. Large castings usually are set in reg- 
ularly to conserve space, care being -taken to fill the spaces 
remaining inside or between large castings with smaller ones 
as far as practicable. As much packing is shoveled in from 
time to time as can be made to run down into the spaces 



192 American Malleable Cast Iron 

still remaining. Extremely complicated work must be placet! 
carefully so that it may be perfectly supported at all 
points. This sometimes necessitates the use of special plates 
and other supporting devices designed particularly for the 
part in question. 

Factors Affecting Heights of Stack 

When the first pot is nearly full a second one is set on 
it and the packing continued as before. The building up 
is continued until the stack of pots is from 3^ to 6 or 7 feet 
high above the top of the stool depending on the height of 
furnace and the ideas of the annealer. Care is taken that 
the top pot be finished Avith several inches of packing into 
which no castings project and usually the top is covered with 
a plate or with fire clay, or both. A reasonable height must 
be attained to secure economy, of space. On the other hand, 
stacks of excessive height are not only difficult to heat uni- 
formly but are subject to careless packing since the packet- 
must stand on a stool and pack in an inconvenient position. 
High stacks also are easily upset in handling. The writer 
favors a stack four pots high where the individual pots are 
12 to 15 inches deep, thus making a maximum height of 
stack of 60 inches above the top of the stool. 

In any event, after the packing is complete and before 
the cover is put on, the stack of pots is rapped with a heavy 
hammer or otherwise jarred to settle the packing solidly. It 
is easy to leave 20 to 30 per cent of voids due to careless 
packing. This not only reduces the capacity but permits the 
ingress of furnace gases and also lets the charge settle, usu- 
ally unevenly. The result is badly warped castings, scaly iron 
.and possibly some completely burned castings in the top 
pots where the packing has sunk away. 

The life of an annealing pot depends somewhat upon 
its composition, but more largely upon the furnace atmo- 
sphere to which it is exposed. Pots which crack from in- 
ternal stresses do so in the first or at least in an early ex- 
posure in the furnace. Thereafter failure is by oxidation of 
the surface, which depends on the thickness of the pot. tern- 



Annealing Practice 193 



perature of the furnace, time the pot is in the furnace, and 
combustion conditions. A life of from only 10 to 12 passes 
is frequent, but the average probably lies between 15 and 
25 passes. Under favorable conditions a pot m'ay survive 
from 30 to 50 trips through the furnace. 

Pots are made either of the same metal used for castings 
or of white cast iron from a cupola operated for that pur- 
pose. In the latter case the mix is usually such as to pro- 
duce a sulphur-manganese ratio which nearly prevents 
graphitization. This is an advantage as reducing the growth 
of pots in use. 

The heating of an annealing furnace is invariably from 
the top down. This causes the top of a stack of pots to heat 
first. It is customary to counteract this tendency by pack- 
ing the light work in the bottom and the heavy work in the 
top so that the greatest thermal capacity is nearest the source 
of heat. 

The packing of castings is a fairly expensive operation 
involving considerable skill which if slighted is productive of 
bad work and loss of castings. 

Various schemes have been suggested for working in 
empty pots to avoid packing. These take 1 the general form 
of a set of plates between the several pots so that the ma- 
trial in the bottom pot does not have to carry the entire 
weight of metal above. Such methods were employed suc- 
cessfully for many years but require careful exclusion of air. 

J. H, Fryer recently introduced a design of separator 
plate as shown in Fig. 89 which by its flanged construction 
permits the making of a good clay seal. While particularly 
important in pots where packing is not used, 'this sealing 
also is required in the usual practice. 

The pots prepared by any of these methods are intro- 
duced into annealing ovens, which are merely fire brick 
chambers capable of being heated to the desired tempera- 
ture. Some idea of the dimensions of these ovens has already 
been given in ithe general description of a malleable foundry. 
Ovens may hold from 25 to 100 stacks of pots, neither ex- 
treme being common. Nearly all ovens are deeper than they 



194 



American Malleable Cast Iron 




Annealing Practice 195 



are wide, and the flame usually travels from back to front. 
A number of exceptions exist more particularly in pulverized 
fuel or oil-fired furnaces. The older ovens, and particularly 
the smaller units frequently were builit in sets of two to 
eight ovens. In this way the loss of heat through the side 
walls and the waste of floor space was minimized. Heavy 
walls about 32 inches thick sometimes were employed to 
serve as heat insulators. More recently, with the advent 
of various types of heat insulating brick the actual wall 
thickness has been reduced. 




Fig. 91. Charging trucks facilitate the handling of pots to and 
from the annealing furnaces 

Many designers laid great stress on heating the anneal- 
ing furnace floors by elaborate systems of checkers or flues 
through which the waste heat of the furnace passed. Other 
designers preferred to use only the necessary flues to carry 
off the flame from the furnace. 

Large Ovens More Economical 

Large ovens are economical of fuel as they present rela- 
tively little wall surface per unit of metal content. However, 
they usually are harder to heat uniformly, and therefore re- 
quire greater skill in design. A number of engineers feel 



196 American Malleable Cast Iron 

that wide arches are expensive to maintain. The relative 
importance of these factors in the mind of the designer usu- 
ally influences the construction chosen in any given case. 
It is not likely that any wide difference in performance is 
to be expected from the possible variations in furnace di- 
mensions. Economy usually dictates the use of a local coal 
for annealing fuel. The firebox design generally is extremely 
simple, consisting merely of an area fenced off in a back 
corner of the furnace by two walls a little higher than the 
stack of pots used. The grates, within this area, are fired 
through the rear Avail. Occasionally, instead of providing an 
inside firebox, the firebox is built outside the furnace against 
the rear wall and communicates with the furnace chamber 
through a fire 'hole, which is like a window through a wall. 

Various stoking devices, including automatic coal feeds', 
shaking grates, etc., have been used, but none of these seems 
to have commended itself sufficiently to gain a firm foothold 
in the industry. Possibly the explanation is that the firing 
operation in ' annealing does not require as careful control 
as in melting. 

It is desirable both in the interest of economy and in 
order to avoid rapid burning of the annealing pots that an 
excess of air be prevented from entering the furnace. How- 
ever with well packed pots the process will be operative, 
though uneconomical, if this precaution is neglected. Thus 
there has been little incentive to control annealing firing as 
closely as the melting operation where the making of good 
iron is impossible with poorly controlled fires. 

Many producers of whom B. J. Walker is considered the 
pioneer, have experimented with pulverized fuel in anneal- 
ing and a good measure of success has attended their efforts. 
The arrangements employed are of the same character as in 
air furnace firing, although the problem is slightly les:;> 
difficult. 

The standard design of annealing oven contemplates the 
introduction of the pots at the front of the furnace. The 
opening is closed by doors, usually made in sections which 
are equivalent to a front wall. 



Annealing Practice 



197 



At an early date attempts were made to render the pro- 
cess approximately continuous. Seth Boyden built a "shov- 
ing" furnace of which G. H. Kings land of the Wilmington 
Malleable Iron Works writes as follows : 

"The furnace was torn down under my direction. The 
pots were 12 inches high and 10 inches wide each way, with 




Fig. 92. The interior of the powdered coal mill of a modern 
malleable plant. The horizontal cylinder at the left is the dryer 



a bottom just like a box without a cover. These were placed 
on rollers, pots being pushed in at one end and shoved out 
at the other. I believe the furnace held 30 of these boxes, 
five wide and six deep. One row of five was shoved out each 
working day and a row of five pushed in. The furnace was 
about 2 feet high at the crown of the arch, with flues under 



198 



American Malleable Cast Iron 




3 O 

M- ,0 



<u ^ 

5 v 

C rt 



Annealing Practice 199 



the floor and in the side walls running to a stack about 25 
feet away through a vitrified pipe. The Barlow people later 
charged the entire furnace at one time instead of at the rate 
of five pots daily." 

Limitations of Removable Roof 

In order to permit the loading of annealing furnaces by 
cranes the design is sometimes modified by forming the roof 
of removable arch-shaped sections, like the bungs in an air 
furnace. In this case no doors are required and the furnace 
is usually submerged in the ground almost to the spring line 
of the arch. 

The heat insulation of the side walls in such furnaces 
is unusually good but heat losses 'through the roof are large 
since the limits of weight prevent the use of a roof of suffi- 
cient thickness. Moreover, the construction involves a great 
number of joints in the roof which are difficult to seal. 
The wid'th of furnaces of this type is restricted 
because of the prohibitive weight of long roof sections. 
Therefore the design is along the lines of a relatively long 
and narrow unit, as compared with the nearly square floor 
plan of the ordinary furnace. 

It is important that the furnace structure be protected 
from the effect of moisture if water is present in the soil 
in which the furnace is set. A story regarding a battery of 
furnaces built near a river subject to spring floods is well 
known in the mallealble industry. To the astonishment of 
their builder, these furnaces became miniature lakes when 
the back water from the first flood rose to a level higher 
than the furnace floor. 

The practice thus far described involves the use of pots 
either with or without packing. Since pots' and packing are 
expensive, efforts have been made to dispense with con- 
tainers, muffle annealing being the outgrowth of these at- 
tempts. 

Muffle-type Furnaces 

Muffle furnaces not "muffled" as frequently pro- 
nounced and even spelled are constructed so that the flame 
from the fire box or burner does not come in contact with 



200 



American Malleable Cast Iron 




Fig. 94. Diagram showing the distribution of heat in a contin- 
uous-type annealing furnace 




Fig. 95. Interior of continuous-type annealing furnace looking 
toward the entrance end 



Annealing Practice 201 



the castings to be annealed. In their general design muffle 
furnaces represent the usual oven with the addition of a 
separate interior chamber or chambers. As usual, the flame 
enters the oven but instead of filling the entire space it 
merely passes through the spaces between the interior cham- 
bers or muffles and the walls, floor and roof. The 
muffles are built as thin as possible usually 4^ inches thick, 




Fig. 96. Single section of combustion chamber of continuous-type 

annealing furnace 



in the interest of low thermal capacity and good heat con- 
ductivity. The castings to be annealed, which must be of a 
character not to distort easily when hot, are stacked in the 
muffles, the front of the muffles bricked up and the oven 
proper closed with the usual doors. The heat treatment is 
identical with that in the ordinary annealing furnace. 

At the conclusion of the treatment the castings are re- 
moved by hand ; consequently the furnace cannot be "pulled" 
until the contents are well cooled. Therefore the output 
of the furnace is decreased by the time taken for cooling to 



202 



American Malleable Cast Iron 




Ecr 



o 

^ b 

*oj o 



(L) O 

A 



rt u 



X! C 

s 



bo. 
tu 



Annealing Practice 203 



this temperature as compared with the time to cool suffi- 
ciently to pull pots mechanically. The thermal efficiency 
also is decreased since the heat must be transmitted to the 
castings through the intervening brick wall. On the other 
hand, the cost of pots and packing and the cost for heating 
pots and packing are saved. 

In view of the fact that the efficiency of annealing fur- 
naces is largely determined by the 'heat insulation of the 
walls and roofs and is consequently widely different in dif- 
ferent plants, it is difficult to speak with assurance as to the 
relative economy of muffle and pot furnaces. The general 
impression toward muffle-type furnaces seems to be favor- 
able. Reliable tests can only be made by weighing coal 
and iron on a series of runs in each of two furnaces of 
identical exterior construction, one loaded with pots the 
other having a muffle built within it. 

The coal consumption for annealing varies greatly in 
commercial practice. .Plants of good reputation burn around 
1000 pounds of coal per ton of iron annealed, although with 
well-built furnaces and particularly with pulverized fuel 
much better records should be obtained. A quantitative 
idea of the heat values involved may be obtained from Table 
XIV, which is based on the theoretical heat requirements of 
the various reactions involved. 

These figures are for the minimum possible use of fuel, 
making no allowance for incomplete or other imperfect com- 
bustion conditions, radiation from furnace walls, heat car- 
ried out by convection currents of cold air when the fur- 
nace is supposed to be cooling slowly, conduction of heat 
into the ground, etc. All of these losses exist and are of 
large magnitude. The aggregate of all losses is what makes 
up the difference between the theoretical coal consumption 
of 274 pounds per ton and the actual commercial figures 
of 600 pounds to 1000 pounds per ton. 

Another way of approximating the radiation and similar 
losses is by considering the fact that an annealing furnace 
of ordinary construction will cool from 1500 to 1300 degrees 



204 



American Malleable Cast Iron 



Table XIV 

HEAT REQUIREMENTS OF ANNEALING FURNACES 

Available Heat of Fuel 

B.t.u. B.t.u. 

Heat value per pound coal 12,500 

Flue gas from 1 pound coal theoretical combustion conditions: 
3.8 pound CO a 

0.4 pound H 2 O 

13.2 pound N 

17.4 Total 
Total sensible and latent heat in flue gas from 1 

pound coal at 1100 degrees above atmosphere 5,000 

Total heat in cinders from 1 pound coal, sensible heat 

and heat of combustion of unburned fuel 160 

Maximum available heat per pound of coal (12,500- 

5,160) 7,340 

Total 12,500 12,500 

Thermal Capacity Oven and Charge 

Total heat 1 ton castings at 1650 degrees above atmosphere 389,400 
Total heat in \ l / 2 tons pots and 1125 pounds packing at 

above temperature 955,350 

Total heat wall, floor and roof 3900 pounds, brick per ton 

charge raised average of 1200 degrees. Fahr 624,000 

Total sensible heat furnace contents per 1 ton casting 

(of this 19.8 per cent only is in castings) 1,968,750 

Heat from Chemical Reactions 

Heat from decarburi.zation 1 ton castings l / 2 per cent or 

10 pounds carbon burned to CO 2 142,200 

Heat absorbed by reaction (10, pounds carbon) 6 FeO + 5C = 

CQ 2 + 4 CO + 6 Fe , 136,360 

Heat evolved by decarburizing per ton of castings 5,840* 

Heat absorbed by graphitization of 2 per cent carbon per ton 

castings. Reaction Fe 3 C = 3 Fe -j- C 53,640 

Heat required to maintain chemical reaction per 1 ton of 

castings 47,800 

Resume Based on 1 Ton Product 

Sensible heat castings 389,400 

Heat of reaction 47,800 

Useful heat 437,200 

Sensible heat furnaces, pots and packing 1,579,350 

Total heat 2,016,550 

Total heat required in oven at 7340 B.t.u. per pound of coal = 274 
pounds coal per ton. 

*Exact decarburizing reactions unknown. Assumption made on 
basis of known composition of resulting gases. 



Annealing Practice 205 



Fahr. in from 25 to 50 hours, depending mainly on the size 
of furnace and the heat insulating ability of the walls. 

The area of walls and roof of an annealing furnace totals 
about 35 to 40 square feet per ton of capacity. With the 
foregoing figures it can be calculated that about 239,000 
B.t.u. per ton of castings must be radiated to cool the furnace 
200 degrees. This at the rate in round numbers of 6800 
B.t.u. per square foot of oven surface (average furnace tem- 
perature 1400 degrees Fahr.) which in turn is at a rate of 
between 136 and 272 B.t.u. per square foot per hour. 

Table XV 

DISPOSITION OF HEAT IN ANNEALING FURNACE 

Total heat in 900 pounds coal at 12,500 B.t.u. = 11,250,000 B.t.u. per ton 
of castings ~ 100 per cent 

B.t.u. Per cent 

Heat for chemical reaction in 1 ton of castings . . 47,800 0.52 

Sensible heat in 1 ton of castings 389,400 3.46 

Sensible heat in pots and packing 955,350 8.48 

Sensible heat in furnace structure 624,000 5.54 . 

Radiation and conduction, furnace structure .... 750,000 6.66 
Sensible and latent heat flue gas (theoretical 

combustion) 4,500.000 40.00 

Heat loss in cinders and air leakage . . . . = 144,000 1.24 

Sensible heat, excess air. error and unaccounted 

for (excess temperature, etc.) 3,839.450 34.10 



Total ' 11,250,000 100.00 

Assuming that 1400 degrees is the approximate mean 
inside temperature while the furnaces is under fire, the oven 
loses heat by radiation and conduction at the rate of be- 
tween 5000 and. 10,000 B.t.u. per hour per ton of contents. 

Therefore with poor insulation the heat lost per ton 
from these sources will be 10,000 B.t.u. per hour that the 
furnace is fired, or 80,000 to 1,200,000 B.t.u. which figure may 
be halved by good insulation. This is equivalent to from 
55 to 165 pounds of coal per ton, an amount insufficient to 
account for all the coal frequently used. The remaining 
losses presumably are due to intake of cold air, excess air 
for complete combustion, excess temperature of outgoing 
air, etc., and other similar losses to be determined only as 
the result of experimental investigation. 



206 American Malleable Cast Iron 

An idea of the heat balance may be obtained from Table 
XV, which is based on an assumed coal consumption of 900 
pounds per ton of castings with only fair insulating and 
combustion conditions. The last item of the table is equiva- 
lent to a little less than 50 per cent excess air. 

It will be noted from the table that only about J^ per 
cent of the heat of the fuel is expended usefully in the chemi- 
cal- changes, which are the purpose of the annealing opera- 
tion, 0.01 per cent in producing the accompanying change in 
volume and only 3j/2 per cent additional in heating the cast- 
ings themselves to the requisite temperature for the reaction 
to take place. 

Obviously the thermal efficiency of the process is ex- 
tremely low, due to the great heat capacity of the oven and 
its contents and to the great amount of heat which is car- 
ried out by the avoidably large mass of gas at fairly high 
temperature. If the alternate heating and cooling of the 
furnace structure could be avoided, if the furnace gases could 
leave the chamber at temperatures lower than that of the 
pots at their maximum and if the sensible heat of the pots 
after anneal could be transmitted to other pots just heating, 
greater economy could be effected. Attempts to do this have 
been shaped in various continuous annealing processes using 
tunnel-shaped kilns. 

The Dressier-type kiln originally designed for use in an- 
nealing sheets and also for use in the ceramic industries 
is just entering the field. Only 3 of these have so far been 
constructed .and, owing to business conditions only one has 
operated for a considerable continuous period of time. The 
principle of operation is that the heat treatment is accom- 
plished by passing the furnace charge, on cars, slowly through 
a long tunnel of relatively small cross section. The tunnels 
are about 300 feet long and the cars of castings or pots pass 
through in- the time required for one annealing cycle. 

Any given part of the tunnel remains constantly at one 
temperature. The temperature varies along the length of 
the furnace to correspond to the changes in temperature 



Annealing Practice 207 



which may be desired as the castings pass through the op- 
eration. Special forms of heating units have been developed 
using oil, gas or pulverized coal which are conducive to 
efficient circulation of the hot furnace atmosphere without 
necessarily contaminating it by admitting the flame itself. 

Heaters Installed for High Temperatures 

The heaters are installed where the highest temperatures 
are required and the products of combustion, leaving them 
at a temperature low enough to make the further transfer 
of heat to pots at their highest temperature impossible, pass 
on and are further used to begin the heating of pots just en- 
tering the furnace and to preheat the air for combustion. 

Further details of construction involve the use pi air 
locks to permit the work to enter and leave the kiln 
without admitting air, the mechanical means of moving cars 
through the furnace, etc. In the absence of any operating 
data on such kilns in malleable practice the effect on fuel 
saving can only be surmised. The principal sources of fuel 
economy which may be expected in a continuously operated 
kiln are the following: 

First, the fact that the furnace structure is neither 
heated nor cooled results in a saving on the basis of our 
previous figures of 624,000 B.t.u. per net ton. Second, the 
fact that since the flue gases and also the product being 
annealed impart much of their heat to the incoming material, 
the loss in sensible heat of flue gases and of pot packing and 
so on should be considerably reduced. Third, the furnaces now 
in use being oil or gas fired, should permit of more economical 
use of fuel than can be had in furnaces fired with coal. 
Fourth, it should be possible to reduce air leakage in a kiln 
of this type far below what could be done in the case of a 
furnace through which the products of combustion are forced 
to pass. 

Offsetting these economies the long slender furnace pre- 
sents a somewhat greater surface per ton of content so that 
radiation losses would increase considering an equal degree 
of heat insulation in the tunnel furnace and in an oven. In 



208 American Malleable Cast Iron 

practice this loss is largely counteracted by efficient heat in- 
sulation on the walls and roof of the structure. 

On the basis of entirely arbitrary assumptions as to exit 
temperatures, flue gas composition, etc., the writer has calcu- 
lated that it might be possible to anneal a ton of castings in a 
kiln of this type with the expenditure of about 2,100,000 B.t.u. 
It must be clearly understood that these figures are speculative 
only, and in no sense founded upon experimental results. 

At the time this is written only one furnace of this type 
has been operated sufficiently long to be considered beyond the 
experimental stage. The best information at the author's dis- 
posal is that in the furnace in question about four million 
B.t.u. 's were required for annealing a ton of product. 

As in the case of electric melting furnace equipment it must 
be remembered that the entire plant layout must be adapted to 
the use of the continuous kiln and suitable provisions be made 
for the transportation of trucks and the mechanical handling 
of material in connection therewith. Also as in the case of the 
electric furnace a very considerable first cost is involved as com- 
pared with the simpler units. Again as in the case of the elec- 
tric melting operation one of the hoped for advantages from 
the use of the more elaborate method is a better control of the 
product, in this case arising from the greater uniformity of 
the heat cycle to be expected in a tunnel kiln operation as com- 
pared with the operation of a furnace which has temperatures 
varying widely, not only from time to time, but also from place 
to place in the furnace. Touceda has designed annealing fur- 
naces of the usual form in which attempts are made to carry 
the elimination of heat Josses as far as practicable. He has 
also suggested a furnace heated by fuel in which the tempera- 
ture Once reached would be maintained electrically by nearly au- 
tomatic means. Such a furnace if practicable would be very 
interesting. At least one concern is attempting to introduce 
an electrically heated furnace. This, however, is decidedly in 
the experimental stage. So much for the practical execution 
of the annealing operation. 

Controlling Annealing Temperatures 

In any annealing operation pyrometric control will be required. 
Thermocouples are somewhat frequently introduced in nichrome or 



Annealing Practice 209 



ceramic tubes through the furnace wall or roof. The practice 
has the advantage of a quick response to changes of firing con- 
ditions and is the only one possible in the continuous furnace. 
However, it does not give any data as to the temperature of 
the metal itself and accordingly it is advantageous to have one 
or more couples actually within the pot. The interior of a 
good sized pot 'may lag 15 or 20 hours behind the furnace 
temperature. The lag is less the more solidly the pot is filled 
with iron and more the greater the per cent of packing. These 
figures apply when the furnace temperature is known and uni- 
form. If the space into which the couple penetrates is filled 
with flame then the flame temperatures, varying as they may 
several hundred degrees in a quarter of an hour or less, are 
absolutely meaningless. Theoretically it may be possible to 
mount a couple in a protection having the same temperature 
lag as an average pot. 

Many satisfactory pyrometric equipments are on the mar- 
ket. Provision for automatic recording is virtually essential. 
The writer's preference is for potentiometer recorders. He fur- 
ther prefers a tape record to a disk record. In large plants 
multiple point recorders are convenient. Noble element couples 
seem commercially undesirable at the temperatures involved, both 
on account of expense and the low electromotive force. In 
oxidizing atmospheres, couples of the chromel type have a good 
life but neither these nor platinum will survive reducing condi- 
tions. Iron-constantan is perhaps most satisfactory under those 
conditions. 

For data on the construction, operation, and characteristics 
of various types of pyrometric equipment reference is suggested 
to Technologic Paper 170 of the United States bureau of stand- 
ards, "Pyrometric Practice" by Foote, Fairchild & Harrison. 

A very brief exposition of principles must here suffice. 

Any thermocouple sets up at its terminals a difference of 
potential, or mill i voltage, depending upon the difference in tem- 
perature existing at the junction of the two dissimilar wires and 
the temperature where these wires are joined to the copper of 
the instrument or distributing system. To know the tempera- 
ture of the hot end we must know that of the cold end. We 



210 American Malleable Cast Iron 

may read this with a thermometer or else keep it constant either 
by burying the cold end in the ground, circulating around it 
water at constant temperature or introducing it into a ther- 
mostat kept at a controlled temperature above that of the room 
by electric heaters automatically switched on and off to main- 
tain a fixed temperature. Boiling water, kept supplied to re- 
place evaporation may be used. 

There are. also electric devices for compensating for "cold 
end temperature." 

The thermocouple electromotive force is measured by a 
millivoltmeter which however actually measures the current 
set up by the electromotive force through the assured constant re- 
sistance of the instrument and external circuit. Since current 
is the quotient of electromotive force divided by resistance the 
readings may be affected just as 'much by changes of resistance 
as by changes of electromotive force. Such changes are coun- 
teracted by making the resistance of the instrument high as 
related to that of the thermocouple and leads. Accidental changes 
of resistance external to the apparatus may be small or even 
negligible fractions of the total. Such high resistance instru- 
ments are difficult to make rugged. Another course is to use 
low resistance instruments and take pains to keep the total re- 
sistance constant. This is possible but troublesome. All indicat- 
ing instruments depend for their accuracy on , c ome torsion mem- 
ber, springs or suspension exactly retaining its elastic .prop- 
erties unaltered. 

The only available means for directly measuring an electro- 
motive force is to oppose it to another variable and constantly 
known potential using a galvanometer only to indicate, by the 
absence of any current when the t\vo are exactly equal. The 
apparatus for doing this is called' a potentiometer. Its use is 
usually slightly less convenient than that of a millivoltmeter 
but avoids all errors except those due to variations in tempera- 
ture of the cold ends. This can also be electrically compen- 
sated. The potentiometer also can be built with a more open 
scale than a millivoltmeter nor need the scale begin at zero, so 
that the scale length available can be used for only that range 



Annealing Practice 211 



of temperature of interest in the process, say 1000 degrees to 
2000 degrees "Fahr. Either type of apparatus can be made au- 
tographic. Although this is slightly more complex for the poten- 
tiometer type this system has the advantage that the motion of 
the pointer is rectilinear and not a circular arc as in the gal- 
vanometer type instruments. 



XI 

PRINCIPLES OF ANNEALING 

A THOUGH the general principles of graphitization and 
decarburization as applied to annealing and the commer- 
cial methods of applying heat treatment to 'castings have 
been considered in preceding chapters, it may be well to correlate 
the scientific principles and commercial equipment with a view 
to providing a more definite practical understanding of the art 
of annealing. 

It has been repeatedly stated in the chapters of this book 
that annealing consists primarily of the conversion of the 
metastable system Fe-Fe 3 C into the stable system Fe-C. This 
involves no change of chemical composition and is not the 
effect of any chemical action on the iron by packing, furnace 
gas or other substances. The only chemical reaction involved 
takes place within the iron carbide or cementite of the iron 
and involves only the chemical elements present within the iron, 
in unaltered amount before and after the reaction : 

Fe 3 C = 3Fe + C 

The reaction involves the absorption of heat (8940 small 
calories per gram molecule) and hence the reaction will con- 
tinue only if heat be supplied. Recent published articles have 
cast grave doubt on the heat of formation of Fe 3 C. Different ob- 
servers do not even agree on whether it is positive or negative. 

In Chap. Ill a detailed discussion of the acceleration of 
the reaction with increasing temperature was given and it was 
pointed out that the reaction is necessarily incomplete at all 
temperatures above the lower critical point of the final alloy. 
The best and most recent data available to the writer has been 
summarized in Fig. 24 in Chapter III and point to a solubility of 
free carbon at A lf considerably less than the eutectoid ratio of the 
metastable system. Below A^ the solubility apparently becomes 
negligibly small but still existant. No evidence of a eutectoid of C 
and Fe as a metallographic entity has been found. 

Metallurgically the purpose of the annealing treatment is to 
cause the iron to traverse such a temperature cycle as will 



214 American Malleable Cast Iron 

completely and most expeditiously transform it into ferrite and 
temper carbon, having due regard to the resultant grain 
structure of the ferrite. The actual heat cycle required to ac- 
complish this result depends upon the chemical composition 
and previous thermal history of the product annealed, 

The control of the annealing oven to produce a given cycle 
is further influenced by the design of the furnace, the uniform- 
ity of temperature throughout, rate of heating, etc. Therefore 
the. art of annealing cannot be taught adequately in a chapter 
of a book. At most the general principles may be outlined, 
it being understood that in practice the operations are shaped 
toward the desired end in accordance with the skill and exper- 
ience of the annealer. 

It already has been shown that the graphitizetion of cemen- 
tite occurs more rapidly the higher the temperature and that the 
rate of this reaction decreases as the reaction approaches its 
end point. Consequently at first glance, it would seem advan- 
tageous to conduct the process in the beginning at the highest 
possible temperature. However, there are practical and the- 
oretical objections to this procedure. The practical objections 
in order of importance are as follows : 

1. The extreme warping or distortion of castings when 
softened by the high temperature. 

2. The sintering or fusion of any available packing ma- 
terial from the same cause. 

3. The wear and tear on the fire brick of the oven. 

4. The decreased service obtained from annealing pots. 

5. The increased fuel cost of attaining extremely high 
temperatures. 

The theoretical reasons are even more important, being: 

1. The large flaky character of the free carbon crystalliz- 
ing out at the higher temperatures. 

2. The poor ferrite structure set up under these circum- 
stances. 

Accordingly the metallurgist must determine for himself 
where the best balance between speed and quality may lie, hav- 
ing regard to the alloys with which he has to work. Opinions 
vary somewhat but the advantageous maximum of temperature 
of castings, as distinguished from furnace atmosphere or wall 



Principles of Annealing 215 

temperature, lies between 1500 and 1700 degrees Fahr. While 
graphitization can be initiated at temperatures far below 1500 
degrees, the reaction at these lower temperatures is prohibitively 
slow without any compensating advantages. Few packings can 
be found which will withstand temperatures in excess of those 
occurring when heating castings to above 1700 degrees Fahr. 
Moreover, the effect on grain structure begins to make itself 
felt at this temperature. 

The reaction at 1800 or 1900 degrees Fahr, is not sufficient- 
ly faster to warrant incurring the increasing difficulties which 
present themselves above 1700 degrees. Many malleable oper- 
ators feel that the extra time required to anneal at temperatures 
not exceeding 1600 degrees is well spent. 

A safe maximum temperature having been determined for 
the particular product under consideration, the annealer first 
directs his attention to attaining this temperature as rapidly as 
possible consistent with a reasonable uniformity of temperature 
throughout the oven. It is here that oven design influences the 
economy and quality of the annealing operations. 

It is unavoidable that those pots nearest the source of heat 
will heat more rapidly than the rest. However, if a furnace is 
designed to permit the rapid and free circulation of flame, the 
differences of temperature will be far less than where such cir- 
culation is hindered to some extent. 

All commercial furnaces have the heat supplied above the 
pots and all well designed furnaces have a sufficient height of 
roof to permit the flame to reach freely to the tops of the 
farthest pots. The author has never heard any annealer ques- 
tion the reason for introducing tlie heat at the top, all seeming 
to take this arrangement for granted. However, there is a 
good scientific reason for this design. The heating of the fur- 
nace contents is accomplished mainly by the vertical gas currents 
in the spaces between the several stacks of pots and to a minor 
extent by conduction downward through the pot and contents. 
If two of the vertical passages between the pots are at different 
temperatures, a gas current will be set up rising in the hotter 
and descending in the colder of the two. Therefore, if the hot 



216 



American Malleable Cast Iron 




Principles of Annealing 



217 




S >5* ^ 

till- 






ttti ' 
$11** 



t 



Mfl 

^ it ^ >i 

r\ iM) N V? 



. 






^^^$ 









m 



218 American Malleable Cast Iron 

gas enters at the top, this circulation will tend to divert the 
descending hot gas from the hotter passages toward the colder 
spaces and thus heat the latter more rapidly. Were the heat 
admitted at the bottom the. circulation described would cause an in- 
crease in the difference of temperature between the hot and cold 
passages since the ascending current in the hotter space would 
draw the hot incoming gases with it. 

Time of Heating Varies Widely 

The rapidity with which an oven can be heated uniformly 
depends entirely upon its construction. A number of observers 
have recorded heating, cycles with pulverized fuel as short as 
18 hours, whereas the author frequently has witnessed periods 
as long as 100 hours and over, usually under adverse fuel condi- 
tions. In some cases the increased time is due to the impos- 
sibility of burning the coal rapidly, while in others the rate of 
downward distribution of the heat in the furnace is the limiting 
factor. In the latter case it sometimes is necessary almost to 
cease firing and allow the heat to equalize by conduction and 
radiation in order to avoid overheating the top pots. This pro- 
cedure is sound metallurgically but necessarily involves a waste 
of time. 

The desired maximum temperature having been reached 
as uniformly and rapidly as possible, the next step is to main- 
tain this temperature until the reactions within the castings 
have attained a state of equilibrium. This time depends upon 
the temperature chosen and upon the chemical and structural 
characteristics of the metal. In experimental determinations the 
time to reach actual equilibrium is long. Under favorable con- 
ditions it may be 20 or 30 hours at 1900 degrees, 100 to 150 
hours at 1500 degrees and several hundred hours at 1400 de- 
grees. In practice the times are materially shorter because a 
slight graphitization of cementite may be relied upon in cooling 
through the higher ranges of temperature and also because 
equilibrium is approached more rapidly during the earlier stages 
than when it is nearly attained. Indeed it might be said that 
actual equilibrium is attained only in infinite time at any tem- 
perature. Under fairly favorable conditions in well conducted 
plants the time to reach equilibrium within commercial limits 



Principles of Annealing 219 

may be roughly as follows: 1700 degrees, 25 hours; 1500, 
50 hours, and 1450, 80 hours or possibly 50 per cent more 
under less favorable conditions. 

These general relationships already have been indicated in 
graphic form in Fig. 36 in Chap. III. The time required 
is approximately inversely proportional to the temperature 
above A^ for alloys high in carbon or silicon the time required 
is less than for those lower in these elements. The presence of 
excessive manganese or sulphur, or of some of the more un- 
usual elements may prolong the time considerably. Also it is 
believed that the rate of freezing and possible other variables 
in the previous thermal history of the metal have an effect upon 
the rate of graphitization. 

The combined carbon content at equilibrium is greater 
the higher the temperature, therefore the iron is not completely 
annealed at the expiration of the required time at the maximum 
temperature chosen. The carbon content, or solubility of carbon, 
as dependent on temperature has been definitely determined for 
metal containing about 1 per cent silicon. The relation is shown 
in Fig. 24. Therefore the anneal will not be complete unless the 
reaction is allowed to progress to equilibrium at or just under 
A\\. The Ar-L point in commercial iron probably is between 1340 
and 1375 degrees Fahr. 

Approach Temperature Slowly 

One way to accomplish the desired result would be to drop 
the temperature quickly from the maximum to just under Ar when 
the reaction at the former temperature is complete and to main- 
tain that temperature below Ar^ as long as may be required to 
re-establish equilibrium at the lower temperature. This opera- 
tion will readily yield perfectly annealed material but is difficult 
to execute in practice except possibly in tunnel furnaces. Under 
commercial conditions, equilibrium can be attained more 
readily just under Ar^ by approaching this slowly from above 
at a rate permitting the graphitization to just keep pace with 
the falling temperature than by a quick drop and a long wait to 
establish equilibrium. Rates of cooling between four and 10 
degrees per hour usually are desired and most operators prefer 
to cool more and more slowly as the temperature drops. 



220 American Malleable Cast Iron 

To make sure of attaining equilibrium a number of an- 
nealers wisely attempt to hold a constant temperature just under 
Ar for some time. Nothing is gained by additional slow cool- 
ing after the reaction at Ar is complete. 

In many plants the cooling rate is determined by the heat 
radiation of the furnace. In these cases the annealer merely 
seals the furnace at the high temperature and lets it take care 
of itself. Fortunately, since the rate of cooling decreases as the 
temperature of the oven falls, a well insulated furnace cooling 
naturally will fall in temperature at a steadily decreasing rate, 
as the metallurgical theory required. Therefore the results of 
this practice often are much better than might be expected. 
Difficulties begin to arise when the cooling is accelerated by 
some unforeseen or unknown cause and the illogical operator 
is no longer able to account for his results. 

It will be noticed that a complete annealing cycle may be 
subdivided into five distinct intervals as follows: Heating to 
maximum temperature, maintaining maximum temperature till 
equilibrium is attained in graphitization of cementite, cooling 
to critical point, holding just under the critical point, and further 
cooling to permit handling. 

The first and last periods have no metallurgical significance 
and can be accelerated as much as is convenient. However, 
the second and the combination of the third and fourth, are 
determined by the product being manufactured and cannot be 
reduced below definite minimum values. The minimum cycle 
is divided as follows: Heating to 1600 degrees, 30 hours; 
holding at 1600 degrees 45 hours; cooling to Ar^ and holding 
there, 35 hours; and cooling to handle, 5 hours. The total is 
115 hours, which would make a six-day annealing cycle as an 
absolute minimum, the time above 115 hours being spent in 
charging and pulling. However, few plants are able to insure 
success in so short a cycle and seven days may be considered 
as the commercial minimum. Cycles of nine days and more are 
not uncommon with large furnaces in order to secure the best 
results. 

The minimum annealing time is fixed by natural laws which 
cannot be changed to suit the wishes of the manufacturer or 



Principles of Annealing 221 

the consumer. Any attempt on the part of the user to hurry 
the producer is misguided. The response to such pressure will 
be in inverse ratio to the conscientiousness and intelligence of 
the particular manufacturer concerned. It would seem that 
self interest will drive the malleable founder to adopt the 
shortest workable annealing cycle in order to avoid the in- 
vestment in additional ovens and their fuel supply. Nevertheless 
the author has known many purchasers of malleable who 
seemed to regard the operation of a long cycle as an arbitrary 
wish of the manufacturer imposed upon his customer without 
any adequate reason. 

For many years the larger producing interests have been 
approached from time to time by frequently sincere but always 
poorly informed inventors claiming either to much reduce an- 
nealing time or sometimes to do away with annealing entirely. 
As a rule, those in the former class expect to accomplish results 
by changes either in furnace design, methods of heating, etc., or 
by some unusual and often secret packing. Being an atomic re- 
arrangement within the metal itself, the annealing reaction can- 
not be accelerated or retarded by the material surrounding the 
casting. 

The laws governing graphitization have been investigated 
by a number of entirely competent experimenters and depend 
on clearly known chemical fundamentals. The design of heat 
treating furnaces also is well understood. Changes in furnace 
design could only reduce the annealing time by accelerating the 
time of heating, since as already explained, the times and tem- 
peratures during the rest of the cycle are fixed by the metal be- 
ing annealed. All of these patented or secret annealing methods 
therefore are foredoomed to failure. 

It is conceivable, although improbable, that someone will 
discover an alloy with a carbon content, similar to that now 
used, of such a character that graphitization. will be suppressed 
at temperatures above 1600 degrees Fahr. but which will graphi- 
tize easily or even spontaneously at lower temperatures. Such 
an invention would accelerate or eliminate the present annealing 
process. Since the alloys of iron with most of the reasonably 
common elements are constantly being investigated and no indi- 



222 American Malleable Cast Iron 

cations have been found of any elements with properties pro- 
ducing the complex effect here described in any degree, it 
seems most unlikely that any greatly accelerated annealing meth- 
od for producing black heart malleable will be found. 

Therefore producers and consumers should admit the 
necessity of adequate time for annealing and conduct their 
several operations in accordance. The author is still waiting 
to hear from a most enthusiastic engineer who, three months 
before this was written, offered to demonstrate the manufacturer's 
ignorance of annealing principles by taking home a sample of 
hard iron in the evening, annealing it over night and returning 
it completely annealed the next day. 

Other incidental changes are produced in the metal while 
graphitization is going an. The clearest evidence that these 
changes are only incidental is the fact that the process of 
graphitization can be carried on perfectly without any gain or 
loss of weight. To prove this, an accurately weighed speci- 
men of hard iron can be enclosed in a tube of difficultly fusible 
glass, the air displaced by hydrogen, the hydrogen pumped out 
to a fairly low pressure and the tube then sealed, so that the 
metal can be annealed surrounded by nothing but a trace of a 
reducing gas. Samples of 10 or 12 grams weight annealed in 
such a tube in accordance with the heat cycle of commercial 
practice, are unaltered in weight to 1/10 milligram. In other 
words, the weight remains constant to 1/1000 of 1 per cent. 

Migration of Carbon 

However, under commercial conditions the castings always 
are in an atmosphere having oxidizing possibilities. This at- 
mosphere may be the atmospheric air remaining in the spaces 
not otherwise occupied or it may be the products of combustion 
or gases arising from reactions with packing materials. There- 
fore there always is a tendency toward burning out the surface 
carbon. The mechanism of the removal is interesting. Only 
the carbon in the outer layer of molecules can combine directly 
with any oxygen in the surrounding gas. Therefore unless 
either the gas can penetrate the solid metal or the carbon can 
migrate to the surface, decarburization would be limited to the 



Principles of Annealing 



223 



infinitesimally small amount produced by burning out the car- 
bon one molecule deep. 

At one time it was generally believed that the gas penetrates 
but the migratory action certainly exists and is probably the 




.01 .oa .03 .04 .05- .06 .07 .06 .09 .10 .// 

Inches Be/ow Surface 



Fig. 99 Increase in carbon content at increasing depths below the sur- 
face of malleable cast iron 

major method by which carbon and oxygen are brought to- 
gether. Carbon exists in iron at any temperature above Ac z 
in part, as a solid solution of a definite saturation value at any 
given temperature. If the carbon concentration is locally low- 
ered below saturation, diffusion will enrich this area at the ex- 
pense of the more highly carburized areas. So long as ce- 
mentite, or undissolved iron carbide remains, the deficit will 



224 American Malleable Cast Iron : 

be made up by solution of additional amounts of this element 
in such a quantity as to maintain the solid solution in a saturated 
state. 

This migration requires considerable time so that in gen- 
eral, carbon is oxidized at the surface much more rapidly than 
diffusion can equalize the carbon content. The result is a ma- 
terial poorer in carbon at the surface than in the center. As 
we go further toward the center, the increase in carbon content 
corresponds to a sort of gradient which is sufficient to feed the 
carbon to the surface as fast as it is removed. 

Fig. 99 shows the increase in carbon content at increasing 
depths below the surface. The graphs represent various de- 
grees of decarburization under commercial operating conditions. 
It will be noted that the graphs vary both as to carbon con- 
centration at the surface and as to the depth of penetration. 
The former depends somewhat on the oxidizing medium em- 
ployed, the latter on the length of time, the medium is applied, 
and on its activity. 

The effect of this decarburization on the physical properties 
of the product are relatively small. Fig. 100 shows graphically 
the results of careful tests made to determine the effect of the 
removal of 1/16 inch of carburized surface in specimens of 
various diameters on the tensile properties of the metal. The 
experiments were conducted by casting tensile specimens to a 
series of diameters, grinding one specimen of each size truly 
cylindrical, removing about 1/16 inch of stock. The ground 
specimens then were annealed with rough specimens from 
the same heat and turned to size after annealing. The graphs 
show the amount by which the properties of the specimen ground 
before annealing exceeds the corresponding properties of the 
turned specimens. 

The experiment was conducted in this form to eliminate 
variations due to cooling rate and original rough surface which 
variables are included in the data given in the chapter on tensile 
strength. 

The tests were conducted on one lot of metal, all annealed 
together. Therefore they correspond to one set of decarburiz- 



Principles of Annealing 



225 



ing conditions only. Since decarburization varies, as the an- 
nealing conditions vary, another series of investigations was 
made to determine the changes in properties in iron of initially 
similar composition by variable decarburization. 




D/omefer Of Specimen Inches 



Fig. 100 Graph showing effect of removing 1/16 inch decarburized 

surface in specimens of various diameters on the tensile 

properties of the metal 

- Results of 50 Tests 

In Fig. 101 have been plotted the results of some 50 such 
tests on iron having from 2.40 to 2.60 per cent carbon, 0.70 to 
0.80 per cent silicon before anneal, which correlate the tensile 
properties with the carbon content after annealing. The graph 



226 



American Malleable Cast Iron 



is plotted from average values. Individual tests depart con- 
siderably from the average since small differences of carbon con- 
tent in the hard iron affect the results much more than much 
larger variations in this element due to decarburization. 



1 




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on Oxidized /.5O U5 WO .7? 
^gAnneo/ino 
*orbon After LO /.Z5 /.50 /,7S 
eal/ng 


Fig. 101 Graph showing effect of varying degrees of decarburization 
on tensile properties of malleable cast iron 



Figs. 100 and 101 serve to show that the final properties are 
relatively little affected by the decarburization process. Be- 
ing measured on surface metal the elongation probably depends 
only in the carbon content near the surface and but little on 
the depth of decarburization. The tensile properties are some- 
what more consistently affected by decarburization. 

Decarburization is controlled in practice by the character of 
the packing material. Perhaps it would be more accurate to 
say that the results in practice depend on the packing used, there 



Principles of Annealing 227 

being but little available information with regard to the action 
of packing. 

The commercial packings depend for their activity chemically 
on the reduction of ferric oxide, Fe 2 O 3 to FeO, ferrous oxide. 
It is not to be understood that they actually liberate oxygen on 
heating as for instance potassium chlorate does. 

Four Possible Reactions 

The process is a chemical reaction in which the oxygen never 
appears as such but merely combines with carbon. Four re- 
actions are possible, depending upon the circumstances: 

3 Fe 2 O 3 + Fe 3 C = 2 Fe 3 O 4 + CO + 3 Fe 

6 Fe 2 O 3 + Fe 3 C = 4 Fe 3 O 4 -f CO 2 + 3 Fe 

Fe 3 O 4 + Fe 3 C = 3 Fe O + CO -f 3 Fe 

2 Fe 3 O 4 + Fe 3 C = 6 Fe O + CO 2 + 3 Fe 

The two reactions 'FeO+Fe 3 C=Fe+CO+3Fe and 2 FeO 
-J-Fe 3 C=2Fe+CO 2 +3Fe are theoretically possible but occur 
only under unusual circumstances, if at all. 

The reaction 3FeO+50O Fe 3 C+4CO 2 can probably oc- 
cur under certain unusual conditions. 

The fact that the analysis of packings is expressed as a 
rule in terms of the Fe 2 O 3 FeO, SiO 2 and possibly A1 2 O 3 and 
other oxides has given rise to the unfortunate conception that 
they are mixtures of two oxides of iron with other inert oxides. 
As a matter of fact all packings in use, as distinguished from 
the raw packing, have become complex silicates. The practical 
annealer unconsciously acts on this knowledge where he limits 
his additions of roll scale, or other raw material to small 
amounts at any one time, for a packing containing any large 
amount of free oxides is not a workable material. 

The raw material from which packing is built up usually 
is roll scale or squeezer scale from rolling mills, pot scale (the 
oxide from the. outer surface of the annealing pots after they 
are drawn from the furnace) or air furnace slag. Iron ore was 
once used but probably is now obsolete. Table XVI shows the 
composition in the usual terms, of these several materials. 

It should be understood, however, that only the first three 
are actually oxides. Ore is nearly pure ferric oxide contam- 



228 American Malleable Cast Iron 

Table XVI 

COMPOSITION OF TYPICAL PACKINGS 

FeO Fe 2 3 MnO SiO, A1,O, 

Ore 00 91.43 8.57 

Pot scale 37.10 53.11 9.79 

Roll Scale 61.47 31.99 6.54 

Squeezer scale 69.74 9.34 .80 14.95 5.17 

Slag 28.80 1.16 4.85 50.42 14.77 

inated somewhat with silica minerals. Pot scale is a more or 
less impure magnetic oxide, Fe 3 O 4 contaminated by sand adher- 
ing to the pots. Roll scale is magnetic and ferrous oxide 
originally nearly pure, but contaminated in gathering it up and 
shipping. Squeezer scale is a mixture of basic silicates of iron 
and manganese with some iron oxides, mainly ferrous oxide 
dissolved in bibasic ferrous silicates. Slag is a neutral silicate 
contaminated with fused brick, etc. 

Some typical analyses of packings as actually used are 
shown in Table XVII both in terms of the usual proximate 
analysis and in terms of the compounds apparently present. 

It will be seen that the packings contain little free oxide 
and are mainly silicates. The ferrous silicates are incapable of 
reduction to metallic iron under the usual annealing conditions 
so that the oxygen for oxidizing the carbon is derived primarily 
from the reduction of Fe 2 O 3 to FeO although the ferrous oxide 
of pot and roll scale may enter into the reaction. 

The relative amounts of carbon monoxide and carbon di- 
oxide formed depend on the temperature and the packing used. 
With the materials and temperature of commercial practice the 
ratio is fairly constant; approximately 12J^ per cent of the car- 
bon being burned to CO 2 the remainder to CO. 

The principal reaction involved, assuming Fe 2 O 3 as the ac- 
tive medium, corresponds to the equation: 

9 Fe 2 O $ -f 8 Fe 8 C = 18 FeO + 7 CO + CO a + 24 Fe 

The actual mechanism of the decarburizing reaction forms 
an interesting though complex problem in physical' chemistry. 
The oxidation of the carbon in the iron and reduction of the 



Principles of Annealing 229 

packing are accomplished by the gas surrounding both. To be 
operative, a system must be chosen so that at the temperature 
and pressure in the .annealing pot the gas phase present is such 
that the reactions 

Fe 3 C + CO a = 2 CO + 3 Fe 

Fe 2 O 3 + CO + = 2 FeO + CO a 

FeO + CO =Fe + CO a 

can all proceed from left to right. In other words the system 
must be one in which a ratio of CO to CO 2 can be maintained 
which will at the same time oxidize Fe 3 C, reduce Fe 2 O 3 , and 
reduce FeO. 

If the relative concentration of CO and CO 2 be such that 
the first reaction ceases or reverses no decarburization will 
occur. If the reaction is initiated it would soon cease, due to the 
conversion of all available CO 2 to CO, unless the second re- 
action continuously reconverted CO to CO 2 . If the last re- 
action reversed, the iron of the casting would be oxidized in 
addition to the carbon in the consequent scaling . Only some 
of the more usual reactions have been considered there being a 

Table XVII 

ANALYSES OF PACKINGS 

Source Pot scale Roll scale Squeezer scale Slag 

Fe 4.04 6.88 

FeO 54.36 57.33 58.49 38.25 

Fe 2 s 9.04 5.97 3.14 1.03 

MnO 1.50 3.03 

SiO, 21.02 26.16 24.92 43.60 

Al a O, and undetermined ..11.54 9.66 11.95 14.09 

Proximate Composition of Above 

Per* cent 

Fe 4.04 6.88 

FeO . 23.40 31.34 21.00 12.60 

Fe 2 3 5.97 1.00 

(FeO) 2 SiO, 40.90 56.90 

(Fe 2 3 ) 2 (Si0 2 ) 3 ..14.10 5.40 

(FeO), (Si0 2 ) a 27.91 ..... 

FeO Si0 2 45.20 

Fe 2 0, (SiO,), .... 5.40 

Various inert silicates by 

difference . ..17.56 27.90 16.70 35.80 



230 



American Malleable Cast Iron 



number of others possible between the components of such a 
system. 

Scientific investigations of the subject matter involved would 
be based on determination of the composition of the gas phase 
in equilibrium with the several oxides of iron and carbon con- 
cerned and a location as to temperature and concentration cor- 




Fig. 102 Equilibrium curves illustrating the reactions between carbon, 
iron and oxygen, after the data of Matsubara 

responding to the reactions proceeding in the desired directions. 
The subject has been but imperfectly studied, the available in- 
formation being mainly due to Schenks' summary "Physical 
Chemistry of the Metals." Matsubara, in a paper presented 
before the American Institute of Mining and Metallurgical 
Engineers, February, 1921, amplifies and checks Schenks' data, 
particularly with respect to the reactions into which the cementite 
enters in the presence of CO and CO 2 . 



Principles of Annealing 231 

Fig. 102 is drawn from Matsubara's paper, based on his own 
results as well as those of Boucourd, Bauer, Schenk and others. 
It represents the percentage of CO in a mixture of CO and CO 2 
for various temperatures at which the several reactions will 
proceed equally rapidly in both directions or at which they 
will cease and equilibrium will be established. The graphs are 
plotted for a pressure of one atmosphere as the sum of the 
partial pressures of CO and CO 2 . For other pressures the 
equilibria can be calculated from the equilibrium constants of 
the several reactions. Letting P be the pressure exerted by 
CO and CO 2 , X the amount of CO in the mixture of these 
gases and K lf K 2 and K 3 the equilibrium constants for equations 
1, 2 and 3, respectively, then 

X* 

K,= P i 

1 X 
X* 

K 2 = P 

\X 
X s 
K,- P 

dxy 

KI K 2 and K 3 can be calculated from Fig. 102 for any giv- 
en temperature and hence the change produced in X by changes 
of pressure at that temperature can be calculated and a dia- 
gram similar to Fig. 102 constructed for other pressures. 

Reaction (4) and (5) are independent of pressure. Un- 
fortunately nothing is known as to the locus of the curves cor- 
responding to (4) and (5) for the silicates forming commer- 
cial packings. The interpretation of the equilibrium diagram 
to determine what reactions occur is as follows: 

On areas below (3) cementite is oxidized to FeO and CO; 
in areas above (4) FeO is reduced to Fe with the formation 
of CO 2 , hence in any region below (3) and above (4), FeO 
will oxidize the carbon of cementite. Such regions exist only 
above 700 degrees Cent., therefore the reaction cannot be main- 
tained at lower temperatures. That the lines (1), (2), (3) and 
(4) should intersect at one point is curious, and indicates that 
at that temperature, pressure and composition, C, Fe, FeO and 
Fe 3 C or any two or more of these radicals can exist together 



232 American Malleable Cast Iron 

in equilibrium. Almost any question as to the course of the 
annealing reaction or the behavior of packings could be answered 
.by the construction of such diagrams for the particular packing 
material. Many conclusions as to the reactions of the pure ele- 
ments and their oxides and carbides will present themselves on 
further study of the diagrams. 



XII 

PATTERNMAKING AND MOLDING 

IN MANY respects, patternmaking and molding practice in 
malleable plants does not differ from that in other branches 
of the foundry industry. The various devices adopted for 
repetitive work in gray iron or brass also are found in use in 
the malleable shop. Indeed, since the producers of malleable 
engage largely in the manufacture of small and moderate sized 
parts in large numbers the development perhaps is further ad- 
vanced than in gray iron practice. However, there are certain 
vital differences between patternmaking and molding for mal- 
leable cast iron as distinguished from the same operations in 
the gray iron trade. These differences arise from the metal- 
lurgical properties of the two materials. 

The two essential distinctions between white iron and gray 
iron lies in the melting point and shrinkage of the two metals. 
Gray iron castings of moderate size are made of metal con- 
taining, for example, 3.25 per cent carbon, 2.00 silicon and 0.50 
phosphorus as compared with the composition of white cast iron 
which approximates 2.50 per cent carbon, 0.75 silicon and 0.19 
phosphorus. The equilibrium diagram for the iron carbon 
alloys shows that all alloys above 2 per cent in carbon finish, 
freezing at the same temperature 1130 degrees Cent, or 2066 
degrees Fahr. It shows further that the point where freezing 
begins varies with the carbon, decreasing nearly uniformly from 
1550 to 1130 degrees Cent, as the carbon increases from nothing 
to 4.3 per cent. 

Leaving the other elements out of consideration, the white 
iron should begin to freeze at roughly 1310 degrees Cent, or 
2390 degrees Fahr. and the gray iron at 1220 degrees Cent, or 
2250 degrees Fahr. 

Thus gray iron will be completely liquid at a temperature 
140 degrees Fahr. lower than that at which white cast iron has 
begun to solidify and .the range of partial solidification or pasti- 



234 



American Malleable Cast Iron 



ness is larger by that amount in white cast iron than in gray 
iron. 

The presence of silicon still further accentuates this point. 
According to Gontermann's data, metal of the composition as- 
sumed for gray iron should begin to freeze at about 1200 de- 





Fig. 103 (Above) Two gates of metal patterns in match part; (below) 

Pattern mounted on match plate and gated pattern 

mounted on vibrator frame 

grees Cent, or 2190 degrees Fahr. and be completely frozen al 
1140 degrees Cent, or 2080 degrees Fahr., whereas white cast 
iron should begin to freeze at 1330 degrees Cent, or 2420 de- 
grees Fahr. and finish the process at 1170 degrees Cent, or 2140 
degrees Fahr. 

The data are not exactly in accord with those based on car- 



Patternmaking and Molding 235 

bon alone, due to minor differences in the observations on which 
the data were based. The point to be clearly brought 'out is 
the higher point of incipient freezing and longer partially frozen 
range for white cast iron than for gray iron. The presence 
of phosphorus in larger amount in the latter still further 
accentuates the difference, although the writer has no available 
data on the freezing conditions in the system Fe-Si-P-0. 

The data given show clearly that white cast iron must be 
poured at a much higher temperature than gray iron, since 
the latter will be liquid at a temperature perhaps 230 degrees 
Fahr. below that where the former has begun to set. Further- 
more, it is quite possible that the fluidity of white iron when 
at a temperature say 100 degrees Fahr. above its freezing point 
is materially less than that of gray iron at the same temperature 
above its freezing point. 

Within the author's knowledge data on this point are 
lacking. A further corollary of the difference in freezing 
conditions is that other things being equal there will be more 
shrinks or porous areas in white than in gray iron castings. 
This arises from the longer freezing range of the former corres- 
ponding to a larger fluid contraction of the still liquid alloy 
between the time and temperature of incipient and complete 
solidification. The consequence of this increased fluid, contrac- 
tion is that as the temperature of complete freezing is ap- 
proached there no longer remains a sufficient volume of liquid 
to fill the voids in the previously formed solid skeleton. 

Therefore, in the last freezing areas, voids remain between 
the dendritic crystals of the first frozen solid. 

The shorter the freezing range the less of this contraction 
can occur. It has been shown by Cesaro that liquid iron is 
a solution of cementite in iron and Wust and Peterson have 
demonstrated that all such alloys freeze as cementite and 
austenite. However, in the temperature interval just under 
freezing the higher silicon and carbon metals graphitize by 
the conversion of cementite into iron and carbon. 



236 



American Malleable Cast Iron 




Fig. 104 Hand operated squeezer-type molding machine and (below) 

mold and pattern equipment in position on machine. Heavier 

machines operated by air also are used in the industry 



Patternmaking and Molding 237 

The iron resulting from this reaction occupies almost 
the same volume as the original cementite. The total volume 
therefore is increased almost by the volume of carbon liberated. 
As a consequence there is a tendency to expansion at these high- 
er temperatures. A number of observers especially Turner have 
recorded actual increase in linear dimensions while the metal 
was cooling and therefore contracting, just under the freezing 
point. 

The expansion due to graphitization is important in two 
respects. It causes the casting to be only about 1 per cent 
smaller in linear dimensions (3 per cent by volume) than the 
pattern instead of double these values for white iron, and also 
tends to fill up in part the voids left by fluid contraction. 

The difference in pattern equipment and molding methods 
in the malleable as compared with gray iron industries is due 
to the necessity for providing against the following differences 
in the properties of the two metals. 

1. The higher melting point and lower fluidity of white 
iron. 

2. Its greater tendency to internal shrinkage due to fluid 
contraction. 

3. Its greater shrinkage from pattern size. 

It will be noticed that the noun "shrinkage" has two 
distinct but related meanings to foundrymen. One refers to 
the reduction in the overall dimensions of the casting as com- 
pared with the pattern and the other to the production of 
porosities due to voids left by the contraction of the fluid metal. 

A distinction based on the words "solid contraction" and 
"fluid contraction" seems desirable but has not- gained favor 
among foundrymen. Accordingly one must be constantly on 
the alert to avoid confusion due to the indiscriminate use of the 
term "shrinkage." 

Speaking first of this property in the sense of solid con- 
traction, the fact that the shrinkage of white iron is about ^4 -inch 



238 



American Malleable Cast Iron 




Fig. 105 Stripper and roll-over molding machines 

(Top) Plain stripper plate molding machine and equipment for cope and drag. 
(Center) Roll-over machine for drag. The cope is rammed up from a plain plate. 
(Bottom) Stripper plate machine for cope and a roll-over machine for the drag. 



Patternmaking and Molding 



239 



per foot instead of ^ -inch per foot as in gray iron does not cause 
any difficulty in patternmaking, except that a proper allowance 
must be made by using a "double" or 54 -inch shrink rule in 
laying out the work in case the casting is to be used hard. This 
shrink rule is merely a rule graduated in feet and inches and 
fractions of inches usually sixteenths in which the distance 
marked as one foot is 12.25 inches. A casting from this pattern 
will come from the mold about true to size. 

Experiment has shown that the solid contraction of white 



n Length in Per Cent of Length at 75 F. 

Co KJ O^ O 




















/ 


















/ 
















. 


/ 
















^sV/ 


/ 
















*4 


\Y 
















^ 


















^ 


















c 


SL 




Total Contraction Independent 
of Chemical Composition.Data 
on Samples of at>out 2^Tbtal 
Carbon No Graphite 


C7* 

0.4 





/ 








/ 


















7 




















00 1600 IZOO 800 400 

Temperatures, Deq. Fahr. 



Fig. 106. Curve showing contraction in cooling from solidifica- 
tion to room temperature 

cast iron (metastable carbon iron alloys) is substantially the 
same irrespective of composition. The contraction in cooling 
from solidification to room temperature, is graphically shown 
in Fig. 106. 

On annealing the casting expands due to the fact that tem- 
per carbon and ferrite occupy a considerably greater volume 
than the cementite from which they are formed. The increase 
in volume and in linear dimensions, depends primarily on the 
original total carbon and to a less degree on the heat treatment 



240 



American Malleable Cast Iron 



by which the graphitization is attained and possibly on other 
more obscure circumstances. 

Some conclusion as to the changes of dimensions produced 
by graphitization can be formed from the following density 
data: Ferrite 7.90, cementite 7.438, carbon 2.30 to 2.70. 

Dimensions Determined by Trial 

The expansion in annealing is usually assumed to be one- 
half the original contraction making the net "shrinkage" allow- 
ance Y% inch per foot as for gray iron. This conclusion can be 
correct for only one particular carbon content. It was probably 



3.10 

500 

0?QO 


\ 




























^X, 


\ 


\. 




























>s 


\ 






















"O 

|2BO 

c 
c270 


_Q 

5260 

25C 

3.40 










X 


\ 






























"S 


\ 






























\ 


\, 










I 
5 


















i 






! 


















f3 


\ 


\ 


1.0 1.10 1.20 130 1.40 1.50 1.60 
Per Cent Contraction of Malleable Specimanfrom Pattern Size 



Fig. 107 Graph showing the per cent of contraction of malleable 

from pattern size 

fairly accurate in the days when high carbon iron was prevalent. 

W. L. Woody has given the writer data obtained in a study 
of over 1000 heats from which test specimens were cast from 
a pattern 12 inches long, the specimens being micrometered 
after annealing. The results are shown graphically in Fig. 107. 
The percentage of net shrinkage of unconstrained specimens 
can.be read from this graph. 

The author has determined the density of hard iron and 
malleable cast iron made therefrom for various carbon contents. 



Patternmaking and Molding 



241 



The data are shown in Fig. 108 calculations as to change of di- 
mensions in annealing from these changes in density yield re- 
sults apparently in error in the direction of too much expansion 
in anneal, i.e. to too small a shrinkage allowance. 

In determining pattern dimensions consideration must also 
be given to the fact that, due to rapping, the molds always are 
larger than the pattern, except on ''stripper plate" equipment. 

On vibrator plates this "rappage" will be small and uni- 
form, in bench and floor molding by hand it will be variable and 
may be large. 

Very small parts may actually require a negative "shrink- 



7.7 



d 

75 
y 

74 

CD 

Q. 

^73 
7.2 





2.3 2.5 2.7 2.9 

Per Cent Carbon In Hard Iron 



3.IO 



Fig. 108 Graphs showing relation of annealing upon the density 

of the metal 

age allowance" "the rappage" exceeding the solid contraction. 
Further it may happen that in irregular and intricate cast- 
ings some parts constrain others when freezing and leave shrink- 
age strains. The relief of these strains during the annealing 
may cause unexpected changes of form. 

Therefore it often is necessary to arrive at the pattern size 
for important dimensions by actual trial and even then the 
castings will come true to size only so long as temperature of 



242 



American Malleable Cast Iron 




Proo>/e for/7?or/bn Of Crock 



Fig. 109 Casting with thin disk and thick hub, showing probable 

point of rupture 

pouring, chemical composition, and sometimes even the solidity 
cff sand and cores are maintained exactly constant. 

The heavy solid contraction of the white cast iron also im- 
poses a number of difficulties which would not be clear to the 
reader were he to consider the problem altogether from the 
standpoint of the net shrinkage of the finished product. It 
has been said that the total contraction of all white cast iron is 
constant. However, it is at least unusual that all parts of a 
given casting cool at the same rate. In other words, in prac- 
tically every casting some parts arrive at their final temperature, 
and therefore final size, ahead of others. This may develop ex- 
cessive stresses or even distort or disrupt the casting. 

Consider a casting having the form of a thin disk with a 
heavy hub at the center, as shown in Fig. 109. The hub will be 
hot and possibly almost fluid when the light disk has already 
set and cooled to nearly room temperature. The contraction of 
the disk during the cooling has met but little resistance from 
the hot plastic center. However, when the latter begins to cool 
its reduction in dimensions will be resisted by its attachment to 




Fig. 110 Type of casting with thin disk center and thick rim 



Pafternmaking and Molding 243 

the solid thin flange. Sometimes this attachment will be so se- 
cure as to permanently stretch the pasty mass within. If this 
cannot occur the flange may be torn loose from the hub 
at one or more places or may even be entirely detached. 

In the reverse case of a thin plate surrounded by a thick 
rim, as shown in Fig. 110, the contraction of the rim would be 
opposed by the previously solidified center, either crushing 
the center or producing a radial tear in the rim. Generally 
the point of failure is at or near the hottest part of the -casting 
Where the strength is the least. Occasionally no external de- 
fect results due to the welding up of such defects by molten 
metal from the center. Then the consequence is a pipe or other 
void. 

The magnitude of the stresses from this source may be 
enormous, depending only on how rigidly the last cooling por- 
tions are held by their solid surroundings. In gray iron the 
difficulty is less pronounced due to the lower magnitude of 
the contraction and to the fact that the solid portions can be 
deformed slightly without breaking, whereas practically no dis- 
tortion is possible in the hard iron. 

Effect on Design of Castings 

The practical application of this reasoning is that, in the 
design of parts to be made of malleable cast iron great care 
must be used to avoid such forms and proportions as will rigidly 
connect parts of widely different cross section. All sections 
should merge uniformly into each other, avoiding abrupt changes 
of thickness. Fairly thin ribs intended to rigidly brace heavier 
sections, spoked wheels with hubs heavier than the rim and in 
general any design in which unequal rates of cooling can set up 
opposing stresses should be avoided. If such designs are suc- 
cessfully executed by the foundryman it is only by methods 'of 
gating or chilling calculated to accelerate the cooling of the 
heavier sections and retard that of the lighter. This calls for 
the exercise of great skill and judgment and may produce pro- 
hibitively higher losses with a corresponding increase in cost. 

We may now consider the shrinkage produced by fluid con- 
traction and resulting in porous material in the areas freezing 



244 



American Malleable Cast Iron 



last. It is impossible to suppress these so called shrinks in any 
casting. Their formation is inseparably connected with selective 
freezing over a temperature interval and hence always occur in 
every casting. 

Depending on particular conditions, these shrinks may be 
widely distributed in insignificant amount at any one place, 
or they may be concentrated in one spo't, aggregating a consid- 
erable volume. A casting freezing at a nearly uniform rate 
throughout, due to equality of section, etc., and freezing almost 
as rapidly as the iron enters the mold may have the porosity 
so uniformly distributed and so nearly filled up from the ladle 
during pouring as to be practically sound. On the other hand, 
a casting having a heavy cross section in some one place which 




Fig. Ill Dendrite (about half size) from shrink in hard iron ingot 

8 inches in diameter by 20 inches high which 

was poured without feeding 



is fluid long after pouring ceases will show a great shrink, 
especially if the heavy section is high up in the mold. 

Two remedies are employed for this trouble. The older is 
the application of iron chills, which are pieces of cast iron 
buried in the mold so that they form its inner surface at the 
points where shrinkage is prevalent. By accelerating freezing 
they suppress the shrink in their immediate vicinity. However, 
since the reduction in volume still exists an equal volume of 
shrinkage will develop elsewhere. This practice is good if 
the shrink in the new location does no harm, or if in that lo- 
cation it can be suppressed by feeding ; otherwise it is merely 
camouflage. Continuously supplying molten iron until the en- 
tire casting is frozen is the only actual preventive of shrinks. 



Patternmaking and Molding 245 

The shrink always is found in the slowest freezing locality. 
Therefore, if to the pattern there is attached a feeder of still 
slower cooling rate so located that metal can flow from it to 
the location in which the shrink was found, then the shrink 
will be transferred to this feeder and be of no consequence, 
since the feeder is not a part of the finished product. The 
actual design of feeders, to meet a given set of conditions may 
require much skill and experience, but the operating principle is 
simple. t 

Feeders are expensive, not only from the molding view- 
point but also because they involve the melting of much ad- 
ditional iron. Nevertheless their use is the safest possible found- 
ry practice to insure sound castings. 

The high freezing point of white cast iron necessitates 
much greater care in gating than is requisite for gray iron. The 
relatively thin gates commonly used for that metal do not admit 
of a sufficiently rapid flow to prevent freezing before the mold 
is filled. Most castings must have metal admitted at a number 
of points in order to permit the mold to fill sufficiently rapidly. 
Because of the large gates, it is necessary to use special means 
to exclude slag or sand floating with the current of metal. The 
thin knife gates of the gray iron industry will choke the stream 
enough to permit these impurities to rise to the surface and be 
trapped in the runners. The same principle is used in malleable 
foundry but greater care is necessary in making the runners 
large and providing places for the ascending slag to be trapped 
on account of the rapid flow of iron required. 

Frequently the iron is poured through a strainer core placed 
at the bottom of the riser, which is intended to cause the latter 
to remain full of metal and allow the slag to accumulate and 
float up. 

(Because of the quick filling of the mold, necessitated by 
the quick freezing of the iron, great care must be used in se- 
lecting molding sands, and in venting the mold. The air and 
gas must be able to escape rapidly enough to allow the iron 
to enter at the rate required to keep it from freezing before 
the mold is filled. 

The selection of molding and core sands of core binders, 



246 



American Malleable Cast Iron 



as well as the actual ramming of the sand are further influ- 
enced by the high solid contraction of white cast iron. The 
mold and cores must be made so as to give readily under the 
heavy contraction of the casting in freezing. If for instance, 
a core be so hard as not to disintegrate before the metal begins 




Fig. 112 Typical gate for malleable castings showing strainer, core 

and skimmer gates for furnishing clean metal for feeders 

and producing sound castings 



to shrink it may set up such a strain in the casting as to actu- 
ally cause rupture. 

The patternmaker can frequently save the customer money by 
a judicious selection of the number of pieces made in one mold. 
A reasonable increase in the castings per mold is good economy. 

f Any attempt to increase the weight per mold by putting in 
so many pieces as to cause pouring difficulties or to prohibitively 
increase the dimensions of the mold it not justifiable. 



Patternmaking and Molding 247 

In general the steps in the improvement of molding meth- 
ods have been as follows: 

Starting with a plain pattern as the simplest equipment, 
the first step was to permanently attach thereto models or pat- 
terns of the gates, feeders, etc., in order that these need not 
be the subject of separate operations. In the case of small 
parts this leads to the mounting of several patterns on one gate. 

To avoid the labor of producing a parting by hand for each 
mold, match parts were introduced, which are merely a semi- 
permanent duplicate of one half of the mold (generally the 
cope). 

In the interests of greater stability plate patterns were 
developed, consisting of fairly thin flat plates, usually of alumi- 
num with the patterns mounted on one or both sides to- 
gether with the gates, etc. The plate being at least as large as 
the exterior of the flask separates the cope and drag by its own 
thickness. Each half of the mold being rammed up off its 
own side of the plate, the mold when closed corresponds in form 
to the parts mounted on the plate. 

To do away with hand-rapping the pattern to withdraw it 
from the mold; air or electric vibrators often are attached. In 
some cases, especially for heavy work, the pattern is with- 
drawn, usually by a lever motion, without rapping, through 
a stripper plate. The stripper plate is merely a plate represent- 
ing the parting of the mold having an opening exactly fitting 
the contour of the pattern at the parting. When drawing the 
pattern downward through this plate the latter supports the 
sand and prevents its following the pattern. 

Unless the cope and drag are duplicates, two machines are 
requisite for each job as the construction is evidently such as 
to be applicable to one-half the mold only for each unit. 

Extremely heavy work is frequently handled on a roll-over 
machine which is especially available for making the drag. After 
the drag is rammed up, necessarily parting downward, the ma- 
chine facilitates turning it over to its proper position by sustain- 
ing and counter balancing most of the weight of the mold and 
pattern by springs. The pattern is sometimes withdrawn 



248 American Malleable Cast Iron 

through a stripper plate and sometimes by letting the mold sink 
away from under the pattern by a suitable lever motion. The 
sand is compacted by hand ramming, by the use of hand or air 
operated squeezers, and by jolt ramming. The latter operation 
consists of mechanically raising the mold repeatedly and allow- 
ing it to come down on a solid support which uses the inertin 
of the sand itself for compressing it. On floor work pneumatic 
rammers sometimes are used. 



XIII 

CLEANING AND FINISHING 

OPERATIONS of cleaning and finishing malleable iron 
castings are conducted in part by the manufacturer, but 
frequently also by the consumer. Some of the simpler 
operations may be dismissed almost with a word but certain 
others such as machining, welding, galvanizing, etc., which are 
performed usually after the castings are delivered to the buyer 
merit more extended discussion. 

Castings generally are cleaned of sand as the first step on 
leaving the foundry. An exception to this is found in some 
cases of large muffle annealed castings where the finish is 
relatively unimportant. Such castings are often annealed with 
out cleaning. In most cases, the hard iron castings are cleaned 
in tumbling barrels, using any of the standard equipment. The 
operation is in no sense distinctive, the only peculiarity being 
the brittleness of the castings. To avoid breakage greater care 
must be used in handling the material and packing the barrels 
than would be needed in gray iron practice. 

Castings of a very fragile character can not be cleaned in 
this manner without breakage. Therefore, it is usual to pickle 
or sand blast them, usually the former. Pickling may be in 
dilute sulphuric acid which loosens the sand largely by the ac- 
tion of the hydrogen gas formed on the surface of the metal or 
less commonly in hydrofluoric acid which dissolves the silica sand 
with but little action on the iron. If the latter acid is to be 
used, economy will dictate the mechanical removal of as much 
sand as possible before pickling to avoid -the needless exhaustion 
of the acid through the dissolving of loose sand. 

Castings Must Be Cleaned 

Large castings are sometimes sand blasted one at a time by 
hand more easily and safely than they could be cleaned by 
rolling. A second cleaning is practically always necessary after 
annealing and this may be by rolling, often using scraps of 
leather, old shoes, etc. to impart a polish. If clean cut edges 



250 



American Malleable Cast Iron 




Fig. 113 Tumbling barrels are used for cleaning castings 



Cleaning and Finishing 251 

are required, sand blasting is often resorted to either in barrels 
or by hand. Pickling is not common except as a preliminary 
to plating. Sulphuric acid, hydrochloric acid, and a hot solu- 
tion of acid sodium sulphate may be used to remove the oxide 
scale left by annealing. 

Since the castings are very likely to become warped during 
the anneal a straightening operation is often necessary if the 
castings are at all complex in shape. 

In many cases, especially on complex and thin work, no 
better method can be used than the hand method. When pos- 
sible a drop hammer fitted with suitable dies may be employed. 
Since the development of arc and acetylene welding, the practice 
of reclaiming defective material by this process has received at- 
tention both by the producer and the consumer. The operation 
of welding has two entirely different aspects, the repair of me- 
chanically unimportant faults of surface and finish in the pro- 
ducer's plant and the repair of castings broken in service. 
Reference will be made later to the latter process, that is welding 
by or for the ultimate consumer. Limiting ourselves for the 
moment to welding as practiced in the malleable foundry, we may 
start with the premise that the founder should deliver to the 
buyer no casting which is not high-grade malleable iron through- 
out. 

In welding, the material of the weld is melted and the cast- 
ing, in part at least, is brought to this same temperature. Thus 
in welding with iron, regardless of whether the filler is 
wrought iron, soft gray iron or any other material, the casting 
will be heated to a point far above the critical point and hence 
on cooling will revert to the condition of white iron.. No in- 
genuity in the selection of a filler therefore will overcome the 
presence of a glass hard spot at the weld. This condition can 
be obviated only by using for a filler either white cast iron or 
malleable, more conveniently the former, although both will be 
white after remelting. If the welded casting is then annealed, 
or re-annealed precisely as in the regular practice the material 
in the weld will be the same as that throughout the casting. 

The temperature of the arc is so high that a thin layer of 
metal can be melted and the operation completed before the un- 



252 



American Malleable Cast Iron 




Fig. 114 Sand blast equipment is used for removing sand from castings 




Fig. 115 Sorting and inspecting small castings are important operations 

in many plants 



Cleaning and Finishing 253 

derlying metal is much heated. The author once had the op- 
portunity to observe the work of an expert arc welder. Work- 
ing on castings retaining their original ferrite surface, this oper- 
ator was able to weld so rapidly using Swedish iron wire, that the 
heat was confined to the ferrite layer and hence a perfectly soft 
weld resulted. Such a result presupposes two conditions not 
usually existing; the first, the use of an extremely skillful 
artisan and the second, a character of repair which does not re- 
quire welding to" a part of the casting below the decarburized 
skin; The latter condition, depending as it does on the char- 
acter of defect to be repaired, is entirely beyond control. 

All Faults Not Cured by Welding 

Whether or not the casting is annealed before welding has 
no effect on the final product and may be left to the welder's 
discretion. Welds made in the above manner by a skilled ar- 
tisan will render the product equal in quality to an initially 
perfect casting. Since the element of skill enters, however, 
it may be a measure of safety to exclude from repair by welding, 
faults which if not perfectly repaired would be the cause of 
serious failures. 

Generally, snagging or the grinding away of gates, fins, etc., 
is the duty of the producer. The operation is performed either 
with the casting in the hard state or after annealing. Usually 
most of these imperfections can be broken off with a light ham- 
mer before annealing and the final finish produced by grinding. 
Grinding before annealing is slower and more expensive than 
if performed on the finished product. But since the former 
method produces somewhat better looking castings, especially 
on sand blasted work, it is sometimes specified when the con- 
sumer feels that this feature is worth the extra cost. 

Hard iron is ground on a very hard and rather fine grained 
emery wheel; malleable is ground on a soft and coarse wheel. 
The size of casting and finish required influence the selection 
of the exact grade of wheel. For malleable grinding wheels of 
artificial alumina, 14 and 16 grit, in a hard grade are used ex- 
tensively. 

The preceding discussion covers the usual finishing opera- 
tions which the malleable foundry performs for its customers, 



254 American Malleable Cast Iron 

however, the customer may perform a number of additional oper- 
ations. Disk grinding, machining, straightening, welding, tin- 
ning, galvanizing, electro-plating, occasionally local hardening 
and possibly other operations come into this category. Since 
the customer's requirements and method are likely to be peculiar 
to his individual conditions, he is better informed as to his 
processes than is the manufacturer of the castings. It will be 
well, therefore, to confine the present discussion to considera- 
tions of the producer's attitude toward these several operations. 
Of the technique of disk grinding little need be said, the 
one essential point to be observed being that in this as in all 
other forms of grinding the operation be not crowded to the 
point where the temperature of the surface metal reaches Ac^ 
Many grinding operations will readily raise the metal in con- 
tact with the wheel to a red heat. A portion of a malleable cast- 
ing which has risen to such a temperature has had some of its 
carbon recombined and has been locally hardened to a degree 
which may render it brittle or unmachinable. 

Should Allow for Finish 

Theoretically, tool life should be long and cutting 
speeds high for malleable cast iron, since the material be- 
ing cut is a dead soft steel which is one of the easiest ma- 
terials to machine. Moreover, the presence of temper carbon 
should favor machining both by breaking up the chip and by 
acting as a lubricant for the chip and tool. 

That this conclusion is correct is indicated by the con- 
ditions under which malleable is machined in practice. In ma- 
chining malleable cast iron not much over 1/16-inch of stock is 
removed at one cut. Only in rare cases are cuts of %-inch to 
5/32-inch necessary in practice. The commercial speeds in lathe 
operation seem to run from 70 up to 160 or 170 feet per 
minute. The heavier cuts usually are run at the lower speeds. 
Fine feeds are commonly used, ranging from .01 to .02 inches 
per revolution. Although generally these conditions are suc- 
cessfully met in operation, machining troubles sometimes are 
encountered. Therefore there is definite reason to believe, either 
that there exists a fairly wide range of machinability in nor- 
mal malleable or that in individual cases an abnormal product 



Cleaning and Finishing 



255 



is unexpectedly encountered in a small amount mixed in with 
a large mass of normal material. 

In the absence of systematic study on the point, no recom- 
mendations are possible by the producer. It is well, however, to 
point out some special features influencing machining. If any pearl- 
ite remains in the finished casting, it is generally very near the sur- 



Pearl/te 

Norma/Structure 



Center of Rotation 
in lathe 




-Finish ed Diameter 
Original Diameter- 



Fig. 116 When machine center and casting center are not concentric, 
apparent hard spots may be found 



face. It is therefore well to design malleable parts with a con- 
siderable amount of "finish" for it is usually easier to remove 
1/16 to 3/32 inches of metal by turning or planing than to 
take a very light cut which may be almost entirely in this 
slightly pearlitic area. At the same time this allowance is a 



256 American Malleable Cast Iron 

necessity to take care of the variations of expansion in annealing 
which are not yet entirely under control of the metallurgist. 

The film of pearlite just referred to sometimes gives the 
misleading impression of hard spots in an otherwise sound 
casting. If the finished surface is not concentric with the sur- 
face of the rough casting is may be that in only a few places 
the lathe tool cut traverses the pearlitic areas which then act as 
hard spots. The fact is that this same area of pearlite exists 
over the entire surface and had it not been that the eccentricity 
in machining threw the cut alternately into ferrite and pearlite, 
no trouble would have been encountered. 

Fig. 116 illustrates this condition on an exaggerated scale. 
Such metal as this, of course, is not of the best quality; the 
manufacturer should and does usually remove this pearlitic lay- 
er. Howeve'r, attention is called to it here to explain the cause 
of complaints sometimes made and to suggest means of using 
such metal which is identical internally with a normally an- 
nealed product when the pearlite is removed by a cutting tool. 

Hard spots in malleable, in the sense of microscopic areas 
containing ungraphitized carbon, and scattered irregularly 
through the mass of a perfect casting are rare indeed. So rare 
is the occurrence that complaints of this fault are found to be 
almost always based on erroneous observation. The symmetri- 
cal pearlite rim just discussed is the most common cause and 
represents not a hard spot at one or two points but a tough 
area of little more than microscopic thickness parallel to the 
surface throughout. 

Shrunken Areas Cause Trouble 

Occasionally, also, a defective casting which for- some rea- 
son has failed of complete graphitization is soft enough to 
machine, though with difficulty. If after most of the machining 
is complete, a tool fails on the casting, the machinist is apt to 
feel that a hard area has just been encountered. In addition 
it occasionally happens that in castings made without suitable 
feeder heads, a machining operation may penetrate a shrink. 
Such areas always show a bright cut and are mistaken for hard 
spots. Cementite in fine granules frequently is present in the 



Cleaning and Finishing 



257 



shrunken areas and dulls the cutting tool if much of the cut 
is in the shrink. 

If the turning operation which penetrates the shrink is 
thread cutting, the threads will crumble away and the metal 
may be regarded as defective when the fault is with the feeding 
of the individual casting. (Both items are to be controlled by 
the foundry but frequently the character of the complaint is 
misleading as to the cause of failure. In the case of threading 
and reaming operations, it is not uncommon to encounter diffi- 




Fig. 117 (left) Cementite psrsisting near a shrink. The metal in 

porous areas is somewhat oxidized. Fig. 118 (right) 

Hard slag inclusions just below the surface 

which may dull cutting tools rapidly 

culties with perfectly normal metal. A metal which has been 
decarbonized considerably may have the entire thread, especially 
if of fine pitch, cut into the pure ferrite rim. Ferrite cuts 
freely, but in rather long chips, hence the flutes in dies, taps 
or reamers may become clogged and prevent a clean cut. In 
work of this character too deep a decarbonization is objection- 
able. 

An interesting operation other than machine tooling occa- 
sionally may be practiced on malleable. This consists of press 
fitting and is accomplished by applying sufficient pressure to a 
casting to bring it to the desired dimensions and perfection of 
surface. To produce reasonable perfect finishes a pressure of 
100,000 pounds per square inch is required. The method is 



258 



American Malleable Cast Iron 




Fig. 119 Malleable casting effectively arc welded with Swedish iron. The changes 
A is soft iron but very slightly recarburized from the malleable; B is an 

carbon due to 




Fig. 120 Hard iron casting successfully acetylene welded with hard iron and 
slag. A is the original casting, B the slag, C the material of weld as noted 

of a little pearlitc 




Fig. 121 Ineffective hard weld of malleable casting using ingot iron wire and 
filler converted into hard iron by migration of carbon from the malleable. 

bitic due to recombination of carbon at 



Cleaning and Finishing 



259 




visible microscopically were insufficient to make notable difference in metal. Area 
oxide or slag film, and C is the malleable showing but little resolution of 
close confinement 




then annealed. Note metallurgical homogeneity of casting except for presence of 
by larger grain size, and D the material of weld as noted by persistence 
due to decarburization 



acetylene method. Neither material has its original structure. A is the soft iron 
B is the original malleable iron, the background of which has become sor- 
temperature the metal reached in welding 



260 American Malleable Cast Iron 

particularly applicable where relatively small objects have to be 
brought to an exact thickness. It is also possible to form 
small objects, for example, radiator nipples in press dies. The 
method is sometimes preferred where it is desired to retain a 
ferrite surface. 

Welding Is Limited 

Welding of broken or defective castings by the user is of 
course subject to the limitations which apply to this operation 
when carried on by the producer with the additional difficulty 
that reannealing is impracticable. Had the consumer facilities 
for the long accurately controlled heat treatments required, he 
could of course weld in the same manner as does the malleable 
founder. During annealing finished surfaces would suffer and 
warping might possibly occur. Under ordinary conditions, 
therefore, welding with iron is not to be regarded as practicable 
as a repair operation. Thus no repair can be made, irrespective 
of the welder's skill, which will restore the original strength of 
the casting. 

The only resource is to braze, that is, to use bronze as the 
welding material. The melting point of bronze is low enough 
to permit operating below the critical point for iron hence 
if care is used a weld can be made without heating the metal 
to a dangerous degree. This, however, involves great skill and 
care on the part of the welder. Ordinary brass, Tobin bronze 
and Parsons' manganese bronze has been suggested as suitable 
for this work. Of course, welds made with nonferrous metals 
do not permit of the complete merging into one another of the 
metal used as filler with the material being repaired. 

They apparently fail invariably by tearing apart between 
the iron and bronze, thus the entire strength of either material 
is not developed. The strongest welds of this type ever tested 
by the writer were made by an expert operator using Parsons' 
bronze. These welds developed an adhesion between iron and 
bronze of substantially 45,000 pounds per square inch thus 
producing a tensile strength of the welded part approximately 
equal to the American Society for Testing Materials, specifica- 
tions for malleable iron. 

The failure occuring entirely along the plane of contact 



'Cleaning and Finishing 261 

between bronze . and iron produced a failure with only a 
negligible elongation, as might be expected. If the circumstances 
are such as to permit making a joint similar in form to the 
wiped lead joint of the plumber, running the bronze up on the 
side of the iron part some distance each way, welds occasionally 
can be made with this metal which develop the full strength of 
the original metal, elongation excepted. Such welds are seldom 
made. A manufacturer of alternating current arc welding 
equipment claims that with his apparatus and a nickel filler small 
machineable welds can be made in malleable cast iron. The 
writer has not yet personally investigated this procedure. 

Work of this character can be intrusted only to very skillful 
artisans. Unusual care and ability are required to produce me- 
chanically perfect welds without even momentary overheating of 
the surrounding metal. Theoretically, there should be no rea- 
son for preferring electric to acetylene welding or vice versa, 
T)ut the writer's observation has been that better work is obtained 
with the gas torch. Possibly this observation may be due to 
the relative skill of the operators whose work has been observed. 

Of straightening operations little can be said here, since 
these operations are in general entirely mechanical. Occasionally 
there comes to the malleable manufacturer's attention heavy 
castings which have been bent in service and straightened in a 
blacksmith's fire. Such castings originate more particularly in 
the repair shops of railroads. Hot straightening is an extremely 
dangerous operation and in general should be avoided by the 
consumer since even severe punishment under a heavy hammer 
will do the castings less permanent harm than an instantaneous 
heating above the lower critical point. The best practice is to 
straighten in a screw or hydraulic press. 

Must Use Accurate Temperatures 

Next to this the use of the lightest hammer blows which 
will accomplish the result is to be recommended. Some castings 
are of such shape that nothing short of a steam hammer will 
do any good. In the absence of properly fitting dies such 
a hammer may so mar the casting as to destroy its utility. Un- 
der these circumstances hot straightening is an advantage but 
-can be executed only under conditions permitting of the use of 



262 



American Malleable Cast Iron 



accurately known and controlled temperatures. Such straight- 
ening should be done at temperatures between 1000 and 1100 
degrees Fahr. At temperatures below 900 degrees Fahr. the 
metal is not sufficiently more ductile than when cold to justify 
the heating operation and at temperatures over 1200 degrees, 
the danger of accidentally overstepping the critical point is so 
great as to be unwarranted. In the absence of pyrometer con- 
trol, hot straightening of castings whose failure would cause 
loss of life or heavy loss of property is almost criminal. 

Application of protective coatings to malleable iron to in- 
crease its rust resistance yet remains for consideration. Pro- 
jection is obtained by a coating of metallic zinc, applied molten 




Fig. 122 Photomicrograph showing heavy pearlitic rim which may cause 
machining difficulties 

as in hot dip galvanizing; by a peculiar form of penetration at 
temperatures below the melting point of zinc, as in sherardizing ; 
and by electroplating as in so-called electrogalvanizing. The 
relative merits of the three systems is so much in controversy 
that it is hardly within the province of the article to attempt any 
decision as between them. It is of course essential to apply 
such a coating as will furnish the maximum protection under 
service conditions. 

The prevalent opinion seems to be that the results of hot 
dipping are in this respect superior to the two competitive 
processes. On the other hand, the author is informed that a 
large consumer of malleable in the form of trolley parts after 
exhaustive tests determined to his own satisfaction the superi- 
ority of the sherardized coating. Another extensive user of 



Cleaning and Finishing 



263 



malleable, who applied his own coating decided upon the electro- 
plating method as being equally satisfactory in service and the 
least liable to injure the product to be coated. 

Hot galvanizing can and should be done without heating 
the metal to be coated above 900 degrees Fahr. Under such 
circumstances there is no reason to fear any recombination of 
the carbon. Unfortunately, however, there are on record a 
number of well established instances in which originally 
perfect malleable castings were seriously impaired by galvanizing. 




Fig. 123 (Left) An effective acetylene weld, malleable becoming sor- 
bitic due to resolution of carbon. A is gray iron converted into 
white cast iron by remelting. B is malleable. .Fig. 124 
(Right) Tobin bronze weld in malleable. Note absence 
of oxides and slag in weld and absence of recom- 
bination of carbon due to relatively low melting 
point of bronze. A is bronze, B is malleable 

Such castings are white in fracture and quite brittle. The fault is 
believed to arise from careless galvanizing resulting in overheat- 
ing of the iron to the point of recombination of the carbon. It 
seems questionable whether a zinc bath could be heated commer- 
cially to above A x . W. R. Bean, as a result of extensive in- 
vestigation, believes that such . recombination of carbon never 
occurs in practice. The writer, and apparently some galvanizers, 
feel that although rare, it can not be said that such a recom- 
bination is commercially impossible. 

However, a very similar variation in quality has been ob- 



264 American Malleable Cast Iron 

served where it was positively determinable that no such over- 
heating has occurred. Indeed, it is sometimes though rarely 
observed in tinning where the temperature is never too high. 
The cause of this well established fact is still obscure. Attempts 
to correlate it with the absorption of hydrogen during pickling, 
with heat treatment alone and with the action of the zinc in 
alloying with iron have all been inconclusive. One malleable 
metallurgist in a preliminary private communication to the au- 
thor expressed the belief that similar deterioration was caused 
in steel and pure iron but escaped notice since the difference 
in the accompanying fractures is less visibly marked than in 
malleable castings. 

Some experiments with various heat treatments at tempera- 
tures far below the critical point would indicate the possibility 
that the phenomenon is associated with the grain structure of 
the material. How these structural changes are produced or 
overcome is still entirely too little understood to permit useful 
conclusions as to operating practice. It appears, however, that 
these faults are rare in sherardized material and have not been 
observed in the electric galvanized product. On the other hand, 
hot galvanizing is so generally successful that it may be con- 
cluded this operation is not necessarily harmful to the physical 
properties of the iron. In the absence of all definite knowledge, 
the malleable founder as yet is unable to do anything to assure 
the success of the operation nor can it be said that any one 
grade of malleable is better adapted to hot galvanizing than 
another. 

The difference in results is more likely to arise from vari- 
ations in the coating process than from the metallurgical char- 
acteristics of the castings. Most manufacturers take the ground 
that they can assume no responsibility for galvanized material 
beyond the delivery of acceptable castings to the galvanizer. 
From time to time also tinners and galvanizers think that they 
observe differences in the way different lots of castings take the 
coating. Occasionally the claim has been made that entire ship- 
ments could not be galvanized or tinned, that is, that the coating 



Cleaning and Finishing 265 

could not be made to adhere. No logical reason for such a phe- 
nomenon seemed evident. All malleable castings consist of the 
same metallographic ingredients, indeed the surface metal is 
in all cases practically pure iron which can be tinned or galvan- 
ized successfully. 

Careful following up of material complained of for this 
reason has disclosed that in no case was the fault with the metal 
itself. Cases occur where the castings have not been cleaned 
properly and hence do not present suitable surface conditions 
for coating. This is at times the fault of improper cleaning 
after annealing and also occasionally due to the formation of a 
rust or grease coating while the castings are handled in 
the consumer's plant. In some cases also the fault has been 
found due to oxidized and dirty zinc or tin baths and to the use 
of tinning alloys too impure to give good coatings. A manufac- 
turer for "many years producing malleable castings which he 
tinned himself in large quantities has assured the writer that 
no cases have ever been found where castings would not take 
the coating perfectly if proper tinning practice is maintained. 

In all that has gone before in this chapter, great stress has 
been laid on the necessity of avoiding even momentary heating 
of malleable castings above the critical point. If such heating 
does occur the carbon instantaneously recombines with iron and 
can be caused to separate again only by a slow cooling equiva- 
lent to that at completion of the annealing process. 

In some few cases advantage is taken of this process to 
reharden malleable purposely. The combined carbon content 
after reheating is a function of the temperature attained; the 
hardness depends on the cooling rate adopted. The result of 
course is a metal of entirely different character from malleable 
iron, the malleability and ductility being entirely lost and a 
new product obtained having some of the general characteris- 
tics of hardened tool steel. Unless conditions are accurately 
controlled, the properties of the resulting metal may be quite 
erratic. To the writer's knowledge, the process has not been 
applied to any important work. Case hardening is said to have 



266 American Malleable Cast Iron 



been applied to malleable, particularly when used for wood 
working tools, but the author is unfamiliar with any such 
practice. However, he has been assured by a consumer that 
quite recently at least two producers still furnished castings for 
edged tools. 



XIV 

INSPECTING AND TESTING 

INSPECTION and testing of the finished product falls some- 
what naturally into two subdivisions, the examination of the 
material as to its metallurgical properties, and the inspection 
of the individual castings for perfection of form, etc. The 
first examination is made generally on the' basis of a system- 
atic control of the works operations without reference to any 
particular castings. Insofar as this inspection is conducted by 
the manufacturer for his own information, but one satisfactory 
system is used. 

This system consists as a minimum in the chemical 
analysis of every heat, either before or at any rate promptly 
after casting and the breaking in tension of at least one test 
specimen from each heat. The chemical analyses are of no 
interest to the consumer. The permanent recording of a test 
from each heat is required by specification A47-19, section lib, 
of the American Society for Testing Materials. 

The maintenance of a systematic record of chemical 
analyses is an almost unavoidable necessity to insure the found- 
ryman against making heats which will not pass the specifica- 
tions. Since test specimens will not come through the an- 
nealing process for 10 to 14 days after casting, they would not 
give warning of bad furnace practice in time to prevent the 
manufacture of a considerable quantity of bad iron. Some dif- 
ference of opinion may exist as to just what constitutes ade- 
quate chemical control of the product, but the greatest weight 
must be laid of course on the control of those elements most 
likely to be subject to dangerous fluctuations. 

Color Method Unreliable 

Carbon and silicon certainly should be determined in every 
heat. The determination of manganese seems urgent in view 
of the fact that in air furnace practice this element is oxidized 
in considerable amounts. The determination of these three ele- 
ments will furnish a check on the mix, or charge, being fed into 



268 



American Malleable Cast Iron 



the furnaces. The fact that in hard iron all the carbon should 
be in the combined state has lead some chemists to the poor 
practice of determining total carbon by color. Since the ad- 
vent of the cheap and rapid direct-combustion methods there re- 
mains no excuse for such a practice. The color method cannot 
be relied upon to give correct values on high carbon metal and 
now survives mainly in consulting laboratories doing cheap 




Fig. 125 Anatytical laboratory in malleable plant 

contract work. While occasional expert operators can consist- 
ently check the correct values to perhaps less than 0.05 per cent 
the author has seen results emanating from supposedly reputable 
laboratories as much as 0.50 per cent in error. An expert 
observer can guess more closely by inspection of a broken 
sprue. Carbon values to be. useful must be within 0.05 per 
cent of correct and should be better. This is only possible by 
combustion methods. Results by color should be disregarded as 
inaccurate. 

With good coal and melting stock, sulphur does not vary 
much from one heat to the next; with poor fuel, however, a 
close control must be kept. It must be remembered that while 



Inspecting and Testing 269 

considerations of speed usually necessitate sulphur being deter- 
mined by evolution, the results on white cast iron seldom are 
exact due to the formation of compounds of carbon, hydrogen 
and sulphur. Oxidation methods also may fail due to the evolu- 
tion of gaseous sulphur compounds. Chrome, in the Aug. 10, 
1921 issue of Chemical and Metallurgical Engineering, presented 
data on this point. The writer's experience is that evolution 
methods seldom give accurate results and may be short 25 per 




Fig. 126 Apparatus for determining carbon 

cent of the total sulphur. Oxidation methods executed carefully 
give the total sulphur but only at the expense of much time. 

The phosphorus content of the metal, in a commercial sense, 
can be predicted exactly from the analyses of the stock, there- 
fore the attention to this element as required by the finished 
product varies inversely as the supe'rvision given the raw ma- 
terial. Prudence will dictate the determination of silicon and 
usually also that of manganese at least in every carload of pig 
iron. The carbon content of pig iron is fairly constant but 
must not be neglected entirely. Sulphur and phosphorus being 



270 American Malleable Cast Iron 

subject to specifications should be watched closely. It seems 
hardly necessary to describe in detail the methods of iron 
analysis which are applicable to hard and malleable iron. The 
procedure of iron analysis is becoming so well standardized 
that mere reference to accepted methods will doubtless give 
the chemist reader the information he requires without burden- 
ing the nonchemical reader with uninteresting data. 

Carbon should always be determined by direct combustion 
in oxygen, determining the CO 2 formed either by direct weigh- 
ing in soda lime or preferably by absorption in standard 
Ba(OH) 2 solution and titration of the excess alkali with stand- 
ard HC1. 

Solutions in which 1 cubic centimeter =^0.10 per cent on a 
1.0000 gram sample are convenient. It is sometimes an ad- 
vantage to add to the sample about 1 gram of carbon-free iron 
before burning to secure better combustion. The use of CuO 
or of platinum black to complete the oxidation is superfluous. 

Silicon is invariably determined by a modification of 
Brown's method substituting a mixture of HNO 3 , HC1 and 
H 2 SO 4 for Drown's method of solution. The major precaution 
is to bake well till SO 3 no long comes off to render SiO 2 
insoluble. 

For manganese the persulphate method of Walters is com- 
mon, finishing the determination either by color or arsenite titra- 
tion. It is well to destroy "combined carbon," that is, the 
colored nitro compounds produced in the reaction of cementite, 
with HNO 3 by oxidation with persulphate before adding any 
silver solution. 

Phosphorus may best be determined by solution in HNO 3 ; 
oxidation, in solution, with KMnO 4 ; precipitation as "phospho- 
molybdate"; and finishing by alkali titration, all in the usual 
manner. Where very few determinations are to be made direct 
weighing of the "yellow precipitate" in Gooch crucibles is con- 
venient. 

Evolution sulphurs are made in the usual way. Rapid 
solution in rather concentrated acid tends toward complete 
conversion of S into H 2 S. It is also a valuable precaution to 
heat the weighed sample for one hour under graphite and 



Inspecting and Testing 271 

allow to cool slowly before dissolving. The graphite must be 
sulphur free. The writer prefers KIo 3 to iodine as a titrating 
solution. 

If the oxidation method is used, concentrated acid and slow 
.solution in a capacious and well covered vessel are desirable. 
This should be followed by evaporation and subsequent bak- 
ing for one hour at not over 400 degrees Fahr. Precipitation 
is made in a cold solution not exceeding 100 cubic centimeters 
in volume containing besides the 5-gram sample 6 cubic centi- 
meters of concentrated HC1 using 10 per cent BaQ 2 solution. 
The solution and filtrate should stand one or two days to allow 
the latter to crystallize. In view of the length of the process care 
must be used to avoid contamination by the laboratory atmos- 
phere. 

Supervise Sulphur Content 

Aside from economic considerations sound metallurgical 
practice would dictate a supervision over the sulphur content of 
the fuel. Taking into consideration the commercial variations 
in fuel, stock and furnace operations, a minimum standard for 
good laboratory control will include the determination of car- 
bon, silicon and manganese in each heat, silicon and manganese 
in each car of pig iron, sulphur in all fuel taking an average 
sample from each group of 5 to 15 cars where coal is delivered 
in large shipments, and occasional determinations of sulphur 
and phosphorus in the product. 

Extending the work to include sulphur in each heat and 
carload of iron, and phosphorus and carbon in each car of 
pig iron sometimes may be well repaid. The analysis of scrap 
material usually is not of value since no means exists for ob- 
taining a true sample. Analytical investigation of steel scrap 
suspected of containing unusual elements is sometimes justified 
when buying scrap direct from the producer. 

Determination of the tensile properties of one bar from 
each heat already has been referred to. The best type of works 
control to insure uniformity of metallurgical quality will in- 
clude a permanent automatic record of all annealing oven 
temperatures. The progressive manufacturer will further avail 
himself of microscopic methods in seeking the cause for defec- 



272 



American Malleable Cast Iron 




Fig. 127 Inverted types of metallographic microscope 




Fig. 128 Detail of inverted type of metallographic microscope (Bausch 

& Lomb) 



Inspecting and Testing 27 Z 

tive material. Methods of metallography yield much valuable 
information relative to the cause of any failures when these 
are due to mischances in heat treatment. 

The metallographic characteristics of hard and malleable 
iron already have been discussed in connection with the metal- 
lurgy of the product. Extended discussion here would amount 
to little more than needless repetition. Messrs. Bean, Highright- 
er and Davenport presented in a paper before the American 
Foundrymen's association in 1920 an extended description of 
"Fractures of Microstructures of American Malleable Cast 
Iron," showing some 40 illustrations mainly of typical micro- 
structures. The interested metallographer may well consult 
the original publication. 

The technique of the microscopy of these materials is in no 
respect unusual. Hard iron is rough ground on an emery wheel 
polished further upon fine emery cloth and finished upon broad- 
cloth charged with rouge. Some operators conduct the inter- 
mediate stages of polishing upon broadcloth charged with F. F. 
F. emery flour and then upon broadcloth and tripoli. The etch- 
ing medium is almost invariably alcoholic picric acid. 

Method of Polishing 

In polishing malleable care is necessary to prevent undue 
deformation of the soft material and the "smudging" of the 
temper carbon. Polishing speeds above 600 feet per minute 
seem undesirable. The specimen is best flattened by milling or 
planing followed by filing and finished as previously indicated. 
Suspended alumina has occasionally been used as the polish- 
ing medium. 

The etching may be with picric acid if pearlite is to be 
examined or usually better, especially if grain boundaries are 
important, with 10 per cent alcoholic nitric acid. A solution of 
nitric acid in amyl alcohol sometimes overcomes a tendency to 
stain. Special reagents such as alkaline picrate or Stead's are 
occasionally required for particular investigations. 

It is well to begin the examination of malleable at 50 or 
100 diameters, to obtain an idea of the form and distribution of 
temper carbon pearlite, etc. At 200 diameters grain size can 



274 American Malleable Cast Iron 

conveniently be studied. The identification of solid solutions 
may require 500 to 1000 diameters and the finer details such' as 
the boundary structures, minute residues of cementite, crystals 
of titanium cyanonitride or nitride can be seen only at 1000 to 
2000 diameters. 

From the manufacturer's viewpoint, inspection and control 
of his product in a metallurgical sense involves chemical 
analyses of raw materials and finished- castings to insure uni- 
formity of product, autographic pyrometer records to insure uni- 
formity of heat treatment, systematic testing of tensile specimens 
to determine the quality attained and metallographic work to seek 
the cause of otherwise unexplainable faulty material. Inspection 
for physical properties of the product when conducted by or 
for the -consumer best can be made in accordance with the Amer- 
ican Society for Testing Materials, specification A47-19, adopted 



I 



-12- 



Fig. 129 A. S. T. M. Tension test specimen 

Sept. 1, 1919. For completeness these specifications are quoted 
in full as follows: 

1 These specifications cover malleable castings for railroad, motor 
vehicle, agricultural implement, and general machinery purposes. 

I MANUFACTURE 

2 The castings shall be produced by either the air-furnace, open- 
hearth or electric-furnace process. 

II PHYSICAL PROPERTIES AND TESTS 

3 The tension test specimens in Section 5 shall conform to the 
following minimum requirements as to tensile properties : 

Tensile strength, pound per square inch 45,000 

Elongation in 2-inch, per cent 7.5 

A (a) All castings, if of sufficient size, shall have cast thereon test 
lugs of a size proportional to the thickness of the casting, but not ex- 
ceeding $/& x %-inch in cross-section. On castings which are 24 inches or 
over in length, a test lug shall be cast near each end. These test lugs 
shall be attached to the casting at such a point that they will not interfere 
with the assembling of the castings, and may be broken off by the in- 
spector. 

(b) If the purchaser or his reperesentative so desires, a casting 
may be tested to destruction. Such a casting shall show good, tough 
malleable iron. 



Inspecting and Testing 275 

5 (a) Tension test specimens shall be of the form and dimensions 
shown in Fig. 129. Specimens whose mean diameter at the smallest 
section is less than 19/32-inch, will not be accepted for test. 

(b) A set of three tension test specimens shall be cast from each 
melt, without chills, using heavy risers of sufficient height to secure sound 
bars. The specimens shall be suitably marked for identification with the 
melt. Each set of specimens so cast shall be placed in some one oven 
containing castings to be annealed. 

6 (a) t After annealing, three tension test specimens shall be selected 
by the inspector as representing the castings in the oven from which 
these specimens are taken. 

(b) If the first specimen conforms to the. specified requirements, 
or if, in the event of failure of. the first specimen, the second and third 
specimens conform to the requirements, the castings in that oven shall be 
accepted, except that any casting may be rejected if its test lug shows 
that it has not been properly annealed. If either the second or third 
specimen fails to conform to the requirements the contents of that 
oven shall be rejected. 

7 Any castings rejected for insufficient annealing may be rean- 
nealed at once. The reannealed castings shall be inspected and if the 
remaining test lugs or castings broken as specimens, show the castings 
to be thoroughly annealed, they shall be accepted; if not, they shall be 
finally rejected. 

Ill WORKMANSHIP AND FINISH 

8 The castings shall conform substantially to the patterns or draw- 
ings furnished by the purchaser, and also to gages which may be specified 
in individual cases. The castings shall be made in a workmanlike man- 
ner. A variation of ^-inch per foot will be permitted. 

9 The castings shall be free from injurious defects. 

IV MARKING 

10 The manufacturer's identification mark and the pattern numbers 
assigned by the purchaser shall be cast on all of sufficient size, in such 
positions that they will not interfere with the service of the castings. 

V INSPECTION AND REJECTION 

11 (a) The inspector representing the purchaser shall have free 
entry, at all times while work on the contract of the purchaser is being 
performed, to all parts of the manufacture's works which concern the 
manufacture of the castings ordered. The manufacturer shall afford 
the inspector, free of cost, all reasonable facilities to satisfy him that the 
castings are being furnished in accordance with these specifications. All 
tests and inspection shall be made at the place of manufacture prior to 
shipment, unless otherwise specified, and shall be so conducted as not to 
interfere unnecessarily with the operation of the works. 

(b) The manufacturer shall be required to keep a record of each 
melt from which castings are produced, showing tensile strength and 
elongation of test specimens cast from such melts. These records shall 
be available and shown to the inspector whenever required. 

12 Castings which show injurious defects subsequent to their accept- 
ance at the manufacturer's works may be rejected, and, if rejected, shall 
be replaced by the manufacturer free of cost to the purchaser. 

These specifications contain a number of points which 
perhaps may be subject to criticism, nevertheless representing 



276 American Malleable Cast Iron 

as they do the consensus of opinion of a committee acting for 
all interested parties and having the approval of a large body 
of able engineering specialists, the specifications* may be con- 
sidered the best practicable solution of the problem of inspec- 
tion of malleable. 

The specifications further have the approval of the Ameri- 
can Foundrymen's association and of the American Malleable 
Castings association. Therefore, it would seem to the best in- 
terests of all that this specification, together with its further 
authorized versions, should be adopted by all producers and 
consumers as a universal guide to quality. Any attempt to modi- 
fy or adapt it to supposed special conditions as a rule will be 









? ' " 


o i " * & 


? ' " 


3 


*-t 


1 


3 J 


1 


1 

|D.a. 


ft 


2 


i" 



Fig. 130 Dimensions of proposed tension test bar 

productive of intolerable confusion and secure no compensating 
advantage. The benefits of standardization will be lost and the 
resulting specification, not having the foundation of mature 
consideration by many minds is likely to be less satisfactory than 
the standard. If in any special case it is agreed by buyer and 
seller that it is to their mutual interest to waive the specifica- 
tions, of course no objections can be made to that course 
provided the understanding is clear to both parties. 

It will be seen that inspection by means of test lugs is prov- 
ided for in the specification. This is a valuable check on the 



^Revisions in the specifications quoted on pages 274 and 275 were 
adopted as tentative at the 1922 meeting of the A. S. T. M. Section 3, 
is tentatively changed to read : 

"The tension test specimens specified in section 5 shall conform to the following 
minimum requirements as to tensile properties : 

Tensile strength, pounds per square inch 50,000 

Elongation in 2-inch, per cent 10.0 

In Section 6 (b}. the following sentence is added: 

"In case one of the retest specimens contains a flaw which results in the 
failure of the bar to meet the specifications, at the discretion of the inspector 
additional test specimens from the same oven may be tested, or test specimens may 
be cut from castings." 

It is further recommended that the standard test specimen be modified 
to conform to the dimensions shown in Fig. 130. 



Inspecting and Testing 277 



quality of individual castings. Test lugs are projections in the 
form of a frustum, of a rectangular pyramid, or of a cone which 
are broken off by the works inspector or by the consumer to 
determine the quality of the metal in the casting. The size of 
these test lugs depends upon the size and thickness of the cast- 
ings to which they are attached. Thus it is impracticable to 
lay down definite rules for their size, form and location. In 
general, lugs should be applied to all castings where quality is 
important. Pieces weighing less than 3 pounds or heavier of 
thin cross section are usually too small to permit of putting on 
a lug and breaking it off without damage to the casting. 

The round test lug is much affected in appearance by 
shrinks and is quite deceptive at times. The author's preference 
is for rectangular test lugs in which the smaller dimension at the 
point of fracture is ^4-inch less than the layer. Generally the 
height of a test lug should be about equal to the larger dimen- 
sion at the point of fracture, and the taper about 1/32 to 
1/16-inch per 1 inch on each side. 

Useful sizes of lugs are specified as follows : 

Dimensions at Dimensions 

breaking point at top Height 

in inches in inches in 

Class of work Length Width Length Width inches 
Very heavy sections 1^4 -inch thick 

and over -K ^ H Jz -K 

Intermediate 5/g ^ -ft & y & 

Light castings up to ^-inch thick.. TS ~fs Yz Y$> . A 

Test lugs, to represent the metal properly, must be free 
from shrinks; hence in general should be located in the drag 
of the mold. In inspecting castings by test lugs, care should 
be used that the lug is not bent in opposite directions to break 
it off. The practice of nicking lugs with a chisel before break- 
ing also interferes with a correct interpretation of the result. 
Under such circumstances the lug breaks off "shorter," that is, 
shows less toughness than it should. 

Three factors must be given consideration in determining 
the quality of a casting from test lug inspection. These items 
are the effort required to break off the lug, the distortion it 
sustains before breaking, and the appearance of the resulting 



278 



American Malleable Cast Iron 



fracture. While the effort cannot be measured and recorded 
in figures, after a time it becomes simple to compare different 
results fairly accurately. In general the hammer should not 
be so heavy as to break off a good lug with one or two blows. 
A fair idea of the energy consumed can be formed from the 
number of blows required to produce fracture. 

The amount of distortion in breaking usually increases 
with the blows required to do the breaking. Test lugs should 




Fig. 131 A 200,000-pound Olsen universal testing machine 

bend out of line materially before fracture. All conditions be- 
ing equal, small test lugs will bend further than large ones. On 
small work where small lugs may be unavoidable, they will often 
hammer over flat before breaking. On heavy lugs a displace- 
ment of 30 degrees will indicate very good material. The inter- 
mediate and smaller sizes listed in the table may bend some- 
what more, even up to 60 degrees. Distortion is greater when 
the break is made by frequent light blows than by a few heavy 



Inspecting and Testing 



279 



blows. Striking the lug alternately on opposite sides of course 
will produce no distortion and hence is valueless. 

The fracture of normal malleable iron, in the absence of 
much compression, is of a velvety black appearance, having a 
mouse gray rim of fair depth. Occasionally two bands are ob- 
served, the outer one being somewhat lighter than the inner. 
The outer rim in such cases, however, is never steely in ap- 
pearance. In bending the lug over, the concave side is of course 
considerably compressed and this compression so distorts the 
crystal structure of the ferrite as to materially alter its appear- 




Pig. 132 Ewing-type extensometer for determining elongation under load 

ance. Toward the concave side of such a lug the fracture will 
be silver white in color and rather fine in grain, that is, not 
coarsely crystalline. This structure may occupy half or even 
more of the entire fracture. However, a band free from any 
steely rim and of normal appearance will always be found 
toward the convex side. 

.When the so-called "compression fracture" is but slightly 
developed, danger exists for mistaking it for a rim unless it is 



280 



American Malleable Cast Iron 



observed that the white edge is along one boundary of the frac- 
ture only instead. of uniformly around it. Lugs broken by being 
struck on opposite sides may show this compression edge on the 
two opposite boundaries and may be difficult of interpretation. 
.They may even be clear white. 

'- Occasionally fractures are encountered which have a so- 
called "picture frame" rim or ''shuck." This is a rim, usually 
of crystalline appearance, completely surrounding the fracture as 




Fig. 133 Olsen-type. torsion testing machine 

a band of uniform width. If the rim is narrow, the material 
may be strong and will bend fairly well. Such rims usually con- 
tain pearlite and the resulting metal is not readily machinable. 
Where machining is no object, a reasonably narrow edge of this 
character need not condemn the product if the lug withstood 
punishment well. Where machining is involved, the inspector 
should use discretion in taking any material with edges in order 
to exclude this condition. 

Entirely white fractures somewhat rarely occur. These may 
be due to an anneal so incomplete that the original hard iron 



Inspecting and Testing 



281 




Fie;. 134 Leeds & Northrup Co. apparatus for determining critical 
points by Roberts Austens method 

structure is but slightly altered, in which case the castings should 
be returned for reannealing. Occasionally the fracture is com- 
posed entirely of steely brilliant facets surrounded by a narrow 
rim of a more gray color. Such iron is useless from the Ameri- 
can viewpoint, being that normal to white heart malleable. It 
is due to radical faults of chemical composition and cannot be 
saved by any ordinary reannealing. 

A further type of white fracture sometimes met with 




Fig. 135 Apparatus for measuring magnetic properties of metal 



282 



American Malleable Cast Iron 



resembles in color and texture the compression fracture men- 
tioned before but extends over the entire fracture. Such lugs 
usually bend but litlte though they are decidedly tougher than 
those defective on account of an incomplete anneal. This ma- 
terial is normal under the microscope and contains no combined 
carbon. The fault lies with the crystalline structure of the fer- 
rite and can be remedied by suitable further heat treatment. 

A coarse black center surrounded by a slate-colored rim 
accompanies weak lugs and is characteristic of poor, high carbon 
material. Considerable experience is necessary to interpret ab- 
normal fractures properly. Indeed, those who pretend off hand 
and from inspection alone to solve all problems as to quality 
of material and causes of failure, usually overestimate their own 
abilities. 

In many cases all the resources of a chemical and metal - 
lographic laboratory are required to diagnose troubles. Since 
the consumer's inspector is not interested in the cause of trou- 




Fig. 136 Farmer fatigue testing machine 



Inspecting and Testing 



283 




Fig. 1.37 Charpy hammer for impact tests 

bles he may be guided in the acceptance of material by the 
following considerations : 

1. Deformation of the lugs must be up to standard. 
2. Bending should require a fair degree of effort. 

3. Irrespective of the fracture, reject all material in which 
the lugs snap off sharply. 

4. Irrespective of a fracture, accept any material in 
which the lug has sustained much more than average punish- 
ment as a result of which indications are rendered worthless due 
to the heavy distortion. 

5. Where machining is to be done, reject any castings 
which have more than a paper thin rim. 

6. Where machining is no object, accept castings with a 
wide steely edge only if the performance of 'the lug under pun- 
ishment is unquestionable. 

7. Reject all castings having a coarse structure and the 
slate colored rim. Such lugs generally are defective with respect 
to the first three tests also. 

8. Return for annealing all condemned castings in which 
the fracture is partially or entirely silver or steely in color. 



284 



American Malleable Cast Iron 



It may be well also for the inspector to assure himself of 
the absence of injurious shrinkage by breaking hard or annealed 
castings from time to time and by watching the fracture of 
heavy unannealed castings for the presence of primary graphite 



f 1 




Fig. 138 Brinell hardness tester 

"mottles." Both shrinks and mottles are found preferentially in 
the last cooling sections. 

Occasionally questions are raised as to inspection for vari- 
ous purposes after arrival of the product at the consumer's plant. 
Except in very exceptional cases, inspection and condemnation 
of entire lots on the basis of faults observed on individual pieces 
cannot be resorted to fairly. As the average malleable found- 
ry is operated, it is quite possible that no two castings in a 



Inspecting and Testing 285 

given sack, or barrel, are representative of the same heat in 
the melting department and oven in annealing. 

The fact that in an impartially drawn sample a certain small 
number of defective pieces are, or are not found proves nothing 
as to the remaining pieces. Therefore, only an inspection piece 
by piece is equitable after the castings can no longer be identified 
with certain specific lots made in the foundry. The test lug 
inspection was devised for this very purpose. Upon occasion 
the problem has arisen of selecting from a large and indiscrim- 
inate mass of castings those too hard to machine. 

Brinell and Shore tests are useless for the purpose unless 
the material is practically unannealed. Some inspectors feel 
that the behavior under a preliminary drilling operation is suit- 
able as a means of weeding out hard castings. Others have used 
the ring of the casting, that is, the pitch of its musical note 
when struck. However, none of these methods are as cheap, as 
simple, or as conclusive as the breaking of a test lug. 

Occasionally it is desired to inspect the finished or semifin- 
ished article to make sure of its fitness for the intended loads. 
Where the maximum loads do not require a proof load beyond 
the yield point of the article, the application of such a load is 
an ideal test. Thus a link belt can be loaded in tension to about 
the yield point and defects which would result in failure under- 
service conditions can be discovered. 

Castings which are straightened after a material deforma- 
tion receive of course a test similar in principle to such a proof 
test. It is therefore hardly necessary to deal with them here in 
any detail. Inspection of castings as to their being true to size 
and form, etc., has not been discussed but this is done by the 
usual methods of gaging and is not different from similar inspec- 
tion on any other product. 



XV 

TENSILE PROPERTIES 

TENSION is the simplest stress which can be applied to a 
material. The ease of execution ,of this form of loading has 
made tensile tests a favorite means of judging the quality 
of a metal even though relatively few structural details are sub- 
jected to pure tension in service. When an elastic material is 
stretched it first lengthens in exact proportion to the applied 
load, in other words, it follows Hook's law of the proportionalit/ 
of stress to strain. Beyond a certain definite loading the stretch 
increases more rapidly than the applied load. The point where 
this occurs, beyond which the material no longer obeys Hook's 
law, is always referred to as the proportional limit. 

In many materials the increasing rate of 'Stretch is at first 
so slight as to escape detection by any but the most sensitive 
of measuring instruments. As more and more load is applied a 
point is usually readied, however, where the material begins to 
elongate very rapidly with practically no increase in the load 
applied. This load is called the yield point and is more easily 
recognized than defined. The term elastic limit, frequently used 
and also frequently misused, signifies that stress up to which the 
material is not permanently deformed. In other words, a 
material may be loaded to any amount up to, its elastic limit and 
when the load is removed will return to exactly its original 
length. This test is seldom employed. Like the proportional limit, 
the elastic limit depends largely on the sensitiveness of the 
available means of measurement. 

Explanation of Terms 

Frequently the three points are confused and used as if 
they were identical- The proportional limit is necessarily below 
the yield point ; how much below depends on the material 



288 American Malleable Cast Iron 

being tested and the accuracy of the measurements. The elastic 
and proportional limits may be considered identical in principle, 
but up to the yield point the permanent set, or elongation, might 
be so small as to escape recognition. 

The reader should remember that by the very definition of 
the proportional and elastic limits the apparent location of these 
points will vary with the available methods of measurement, the 
proportional limit being the largest load the material will sustain 
without visible departure from Hook's Law, and the elastic 
limit the largest load it will sustain without taking a permanent 
set. The greater the precision of the measurement, the lower will 
be the stress corresponding to these definitions. Doubt is fre- 
quently expressed whether cast metals actually have any propor- 
tional limit larger than zero, the thought being that with suf- 
ficiently delicate extensometer measurements, the graph would be 
a curve from the origin. In view of these facts an attempt to 
find the elastic limit by watching the drop of the testing machine 
beam will give apparently higher values than determining this 
point by the divider method and the divider method will give 
materially higher results than the extensometer. The engineer 
will therefore require to know how these points have been 
determined in making intelligent use of the information. 

Action of Metals in Tension 

Most ductile materials when loaded in tension beyond the 
yield point do not stretch uniformly at all points of their length. 
The larger part of the deformation usually occurs quite close to 
the point of failure. The specimens accordingly neck in and finally 
break at the smallest portion of the necks. The per cent of elonga- 
tion is therefore less the longer the gage length in which it is meas- 
ured. The difference between the area at the point of fracture and 
the original cross-sectional area, expressed in per cent, is called 
the reduction in area. A high reduction in area is even more indi- 
cative of a very ductile material than a high elongation. The ratio 
of stress to strain, below the proportional limit, is known as the 
modulus of elasticity- These various constants, proportional 
limit, yield point, elongation, reduction in area, modulus of 
elasticity, and ultimate strength and the relationships between 
them give a very good picture of the behavior of any material 



Tensile Properties 



289 



under static loads. These constants also yield some information 
regarding its behavior under dynamic stresses. The application 
of each constant is fairly evident. The proportional limit is 
useful when the deflection must be temporary and predictable. 
The yield point limits the stresses which may be applied with- 



50000 



40000 



b 30000 
c. 



20000 



10000 



Curve A' 
Curve B- 



Specimen; 

Diameter = 0. 
Gage length* 5 




004 

0.0004 



0.06 
0.0006 



0.08 
0.0006 



0.10 
00010 



O.IZ 

o.oo ie 



Unit" Elongation 



Fig. 139 Stress-strain diagram of malleable cast iron in tension 



out producing visible 'permanent changes of shape in the mater- 
ial. Elongation and reduction of area are indicative of the amount 
of distortion a material can stand without fracture. The ultimate 
strength measures the load that can be sustained without failure, 
although with permanent deformation. The modulus of elasticity 
serves to determine the elastic deflection under relatively small 
loads. The behavior of a material under tension is most con- 
veniently expressed by means of a stress-strain diagram, in 
which the elongation in per cent in some definite gage length is 
plotted against the increasing load in pounds per square inch. 
Fig. 139 shows a graph of this kind somewhat typical of malle- 



290 American Malleable Cast Iron 

able cast iron. The various constants are marked in the graph in 
the appropriate places. The curve is made from a malleable 
casting about the tensile strength .prescribed by the A. S. T. M. 
specifications. 

Malleable iron of higher tensile strength would have the 
proportional limit, elastic limit, and yield point raised very 
closely in the same proportion as the tensile strength increased. In 
other words, fhe proportional limit would always be about one- 
third of the ultimate strength and the yield point as measured 
by extensometer about six-tenths the ultimate strength. The 
yield point determined by the divider method will be about two- 
thirds of the ultimate strength. 

The tensile strength of malleable cast iron, as measured in 
a test specimen of specified form and dimensions s'hould be 
45,000 pounds per square inch and its elongation in 2 inches 
7 l /2 per cent according to the 1919 specincatioins of the American 
Society for Testing Materials. The specimen is to be of the 
form and dimensions shown in Fig. 129. The apparent tensile 
strength of this, as of any other cast product, is affected by the 
gating of the castings forming the test specimen. This is not 
due to any effect on the properties of the metal as such, but 
on the degree of soundness wlhich is secured in the casting. 
Obviously, to give representative results it is necessary to take 
such precautions as may insure the freedom of the specimen 
from shrinkage. 

Specimens Must Be Representative 

The point seems worthy of discussion in this chapter be- 
cause criticism and confusion often arise when specimens cut 
from castings or parts of castings do not conform in properties 
to the American Society for Testing Materials specimens from 
the same heat. The discrepancy frequently is due mainly to inter- 
nal defects of the castings from which specimens are taken. 

Failure of 'such specimens to pass the test indicates im- 
properly fed castings ratiher than weak metal. The tensile 
strength and elongation of malleable as made today by the lead- 
ing manufacturers exceed the American Society for Test- 
ing Materials specification by a safe margin, the metal now 



Tensile Properties 



291 



sold by reputable makers rarely being under 48,000 pounds per 
square inch' in tensile strength and 10 per cent in elongation. 
The product probably averages about 51,000 pounds ultimate 
strength and 12 per cent elongation. 

The tensile strength and elongation of daily specimens 
submitted by all of the more than 60 members of the American 
Malleable Castings association have been averaged by months 
and the results plotted as shown in Fig. 140. The recent data 
average better than the author's personal estimate. 

Occasional record performances have been noted. The 
highest grade malleable known to the writer was a single piece 
having a strength of 58,000 pounds per square inch, and an 
elongation of 34 per cent. A strength of 64,000 pounds coupled 
with an elongation of 18 per cent was once noted. These were 
single isolated cases and in no sense typical of a routine product. 
One plant produced castings over 57,000 pounds ultimate 
strength and 20 per cent elongation continuously for about a 
month. 

As might be expected from its microstructure, the tensile 
strength of malleable cast iron is largely dependent upon its 
carbon content, since the more carbon the greater the interrup- 
tion to the mechanical continuity of the casting. This applies 
rather to the original carbon content than to that after anneal. 
Carbon once liberated has accomplished its destruction of con- 
tinuity and even if it can be removed after formation, it leaves 
behind the hole it occupied. 

Furthermore, the other elements present besides carbon 
may affect the physical properties of the ferrite just as they affect 




Fig. 140 Tensile strength and elongation plotted from specimens 
submitted by members of American Malleable 
Castings Association 



292 American Malleable Cast Iron 

the properties of a dead soft steel. This, however, is of less 
practical importance than the variations due to carbon, since 
within 'the limits capable of commercial annealing none of the 
other dements are likely to have an effect of the order of 
magnitude of those due to the latter element. The writer in the 
past has had occasion to make comparisons of the tensile proper- 
ties of many thousands of 'heats with their chemical composi- 
tions. As a rule investigations of this character are influenced by 
so many variables that a summary which is strictly accurate as 
well as fairly simple is hardly possible, save at the expense of 
space for detailed technical explanation which could be spared 
only in a monograph upon that one subject. 

Increased Carbon Lowers Strength 

In general it may be said that an increase in carbon always 
carries with it a decrease in strength and elongation. The de- 
crease in strength per unit increase in carbon is greater the 
greater the total amount of carbon and the higher the silicon- 
Manganese and sulphur when present in correct relative 
proportion and within anything resembling commercial limits 
have relatively little effect. Phosphorus up to about 0.20 or 0.25 
per cent strengthens the metal without decreasing its ductility. 

The considerations just /outlined would seem to furnish a 
basis for a graphical or tabular summary of the relation be- 
tween tensile strength and chemical composition. The great dif- 
ficulty is that even though the effect of each element may be 
well established, there remain variables due to the form of test 
specimen, the soundness of the specimen and the effect of the 
previous thermal history on the physical and grain structure of 
the ferrite. 

Accordingly the presentation of such a summary might be 
misleading to the interested user of malleable and would serve 
:no useful purpose as a guide to specifications or to successful 
practice, unless the other variables could also be successfully 
defined and prescribed. As a guide to the general order of 
magnitude of the effect of carbon and silicon on normal 
malleable iron, Fig. 141 shows the average tensile strength of 
malleable of varying carbon content but of constant silicon as 



Tensile Properties 



293 



averaged from a large number of heats. An increase of 0.01 per 
cent silicon decreases the tensile strength about 20 pounds per 
square inch for low-carbon iron (about 2.25 per cent), and 
about 75 pounds per square inch high-carbon iron (about 3.25 
per cent). From these data it would seem that a simple arith- 
metical calculation should show what the strength of malleable 



54000 
c ^nnn 


Per Cent C 
235 .40 45 .50 .55 I. 


arbc 

DO U 


>n Before Annea 
>5 70 .75 j50 21 


I 

J5 .90 .95 3. 


30 




* 


B= 5=^ 


^ 


^ 






















^stooo 

o 

51000 

50000 

0-49000 
tf> 

i_ A o nr\r\ 












X 


x 






























^s 


^ 
































\ 


v 






























\ 


^, 






























\ 


V 








Q)40WV 

CL 
























\ 


V 






TJ 

46000 



^45000 

AAC\f]C\ 






5il 


icoi 


i = 


,75 PerCer 


t 








\ 
































\ 
































\ 


43000 































































Fig. 141 Effect of carbon on tensile properties of malleable iron 

cast iron in pounds per square inch measured in the American 
Society for Testing Materials test specimen should be for any 
given composition. 

Any attempt, however, to apply these figures literally is 
not likely to be productive of results, since the formula is purely 
an empirical one and since no account is taken of some of the 
other variables, notably of the effect of heat treatment in the 
properties of ferrite. 

Malleable iron, when completely annealed, stands alone 
among the ferrous materials in that variations of composition 



294 American Malleable Cast Iron 

affect the elongation in the same direction as the strength. 
That is, malleable cast iron has a higher elongation the greater 
its strength. 

The reader should not lose sight of the fact that what has 
just been said concerning the proportionality of tensile strength 
and elongation is only true of completely graphitized 'products. 

For many years and up to relatively recently misguided 
efforts were made by ill-informed or careless manufacturers 
to produce a metal of great strength by using a chemical com- 
position or heat treatment calculated to produce incomplete de- 
composition of the combined carbon. The resulting metal is, of 
course, stronger than good malleable cast iron, since the matrix 
is more or less pearlitic instead of pure ferrite; and also since 
less temper carbon is formed by the amount remaining combined 
in the matrix. However, the relative lack of ductility of the 
pearlite, interrupted as it is in addition by temper carbon, ac- 
counts for the lack of elongation shown by material of this 
character. The elongation may fall as low as 2 per cent in such 
cases- 

High Strength May Be Deceptive 

Material in which a strength approaching or exceeding 60,- 
000 pounds per square inch is observed, without a correspond- 
ingly good elongation (at least up to the average or preferably 
as high as 12 per cent or 15 per cent) should be looked on with 
grave suspicion as not being the product of well controlled 
malleable practice. 

Each circle in Fig. 142 shows a group of heats of a given 
analysis, the different circles representing different analysis. 
They are located according to the strength and elongation of 
the resulting product. It is plainly evident that increasing 
strength is accompanied by higher elongation. This graph fur- 
nishes some basis for conclusions as to the effect of chemical 
compositions on elongations by demonstrating the approximate 
proportionality of f the two properties. An exception has been 
noted in that while silicon slightly decreases tensile strength 
and hence should decrease elongation, the reverse is true for 
very low silicons, especially in the presence of low carbons. The 



Tensile Properties 



295. 



departure may perhaps be explained in the light of minor inter- 
ferences with complete graphitization. 

The tensile strength of malleable iron further varies with 
the cross-^sectional area of the piece under ; consideration. This 
phenomenon is not due to the long-exploded thought that the; 
strength of malleable iron its only in the skin. This thought 
persisted from the days when malleable iron was made; 



JWUU 

. E 50000 
ST 

& 

_> 

lUsCOO 

I 
t/) 
j> 

40000 
35000 






















/ 


s 


















8 

,J 


f*. 



















< 


y 


A 

o 




















^ 


/ 


















_>^ 


y 




















,/ 


/ 




















\/\ 


^ 


















/ 


/ 






















> 7 6 9 10 II \Z 

Elprrcjation in 2 in T percent 



Fig. 142 Relation between tensile strength and elongation of mal- 
leable cast iron 



"malleable" by decarburization only, as is the case with the so- 
called "white heart" product of Europe. 

The skin of normal American or black heart nfalleable dif- 
fers only in degree from the center. W. R. Bean* gave figures 
indicating that specimens from the same heats tested in their 
condition as cast and after machining off at least 1-16 inch, and 
sometimes % inch of the surface, had practically the same 
strength. Tests made by the writer indicate that on 'sections 'up 
to one inch in diameter, after machining, the ultimate strength 



*Piaper -presented at the annuad meeting of American Society for 
Testing Materials, 1919. 



296 



American Malleable Cast Iron 



8000 
7000 
"I 6000 

ISOOG 
f- 4000 

^ 3000 

c 

Jzooo 

1000 







^ o - ro ^ ^ 

Percent j 














Not 


?. Data Plotted are the Difference - 
v<?w Constants for Rough Specimens 
1 Constants for Turned Specimens. 








^^ 


2si 




beh 










1 


%s 














'- 


^i 
























%\ 


























%s 












~^T^ 












^v 










^6 










^v 














Z^feg, 








? 


Sw 




















V, 




1 1 1 

Diameter as Tested, n. 



Fig. 143 Comparison of tensile properties of machined and cast 
specimens of equal diameters 



of bars with the original skin is about 4000 pounds per square 
inch higher than on bars from which the skin has been turned. 
The value given varies with the size of the specimen, as shown 
graphically in Fig. 143. 

The yield point is not affected measurably by turning off 
the surface. The elongation, however, is materially affected, 
being decreased 3 or 4 per cent by the removal 'of the surface. 
In the case of thin sections, turning off the surface reduces the 
reduction of area 5 or 6 per cent and in extremely thin speci- 
mens considerably more. It will be seen that these differences, 
although not by any means negligble, are not of an order of 
magnitude to warrant the conclusion that the properties of the 
surface metal are all that gives malleable cast iron its value. 

The difference in unit strength between large and small cross 
sections may be due to either of three general reasons. The 
large specimen may not be so molded and poured as to be free 
from shrink. This difficulty usually can be avoided in castings by 
proper feeders, unless the casting be of especially intricate de- 
sign. In test specimens this remedy can always be applied because 
in this case commercial molding restrictions affecting produc- 
tion never apply. Even when this difficulty is entirely overcome 



Tensile Properties 297 



there remain two other variables which always prevent a large 
section from having the same strength in pounds per square 
inch possessed by a small one of the same metal. 

Both of these variations arise from the cooling rate of the 
casting. The rate of cooling of the casting in the molds affects 
the final product by its effect on the formation of primary 
graphite and by its effect on the grain structure in the hard iron. 

The former difficulty is easily suppressed by making the 
chemical composition such that no graphite will form on freez- 
ing, even when the cooling is as slow as any to be expected. Even 
when it is completely overcome, as is usually the case, the effect 
on grain structure persists. The size of the ferrite grains in 
malleable in a large measure is determined by the graphitizing 
heat treatment, although perhaps not to the exclusion of the 
freezing conditions. However the size and distribution of the 
temper carbon nodules is largely an expression of the concensus 
of fineness of the original dendritic structure of the hard iron. 

Iron alloys in crystallizing while freezing obey the same 
laws as do all other crystalline solids in that slowly growing 
crystals are larger whereas quickly formed crystals are small. 
Consequently a large casting always has a coarser structure 
than a small one made of the same metal and to a slight extent 
the surface of any casting will be of finer grain than the center. 

These differences are carried over into the annealed product 
since the form and distribution of the cementite will more or less 
affect the distribution of the ferrite and temper carbon into 
which it breaks up, hence the quickly cooled casting will have 
finer and more uniformly distributed grains of free carbon than 
one cooled more slowly. Fig. 144 shows the strength and elonga- 
tion of specimens varying in diameter from % to 1.5 inches. 

A further word of caution may be necessary. It has just 
been explained that of the same metal a small specimen is 
stronger than a large one. It is quite possible, at least within 
limits, to produce a metal of any desired strength in any given 
section even if that section be large. Thus castings having a 
cross section 4 l / 2 x 9 inches have been produced experimentally 
with the material at the center having properties conforming to 



298 



American Malleable Cast Iron 



55000 



50000 



e 

Or 

? 45 000 

& 



40000 



35000 





Diameter, in., as Cast. 



Fig. 144 Results of tests on specimens not machined 

the American Society for Testing Materials requirements. Re- 
duction of airea is not frequently determined on malleable cast 
iron since the material is tested without machining. The im- 
possibility of determining the area of a comparatively rough 
specimen before testing precludes the determination of this 
constant under standard conditions. Occasionally the author has 
determined this constant for specimens ground truly cylindrical 
before annealing. The following table give's an idea of w'hat 



. Tensile Properties 299 

may be expected when the specimens are a'bout ^ inch in 
diameter. 

Ultimate strength in Per icemt of -elonlgation Reduction in area 

pounds per square indhi in 2 iniches in per oent 

51,600 21 18 

51,500 20 17 

55,200 19 18 

55,100 13 20 

55,200 17 23 

In malleable cast iron, as in other materials, the reduction in 
area decreases as the diameter of the specimen increases. It is 
a general principle that the reduction is greater the fewer grains 
of iron are contained in the cross section. 

In a certain series of tests on a given metal the following 
results were observed: 

Diameter Reduction in area 

indies per cent 

*/ 4 28 

M 20 

*A 18 

M 14 



Castings Not in Tension 

In engineering design malleable castings are seldom sub- 
jected to pure tension. Loads in cross bending, compression 
and in shear are much more common. Indeed, where tension is 
applied to malleable castings the load usually is transmitted to 
the casting by screwing the latter into a nut or similar detail. 
Typical cases are malleable eyebolts in turnbuckles. Although 
the -shank of the bolt may be in tension, consideration must also 
be given to the shearing strength of the threads where 
strength calculations are requisite. Unless the design of 
such bolt-like details is such that the threaded end has 
an outside diameter sufficiently larger than the shank's diameter 
so that the area at the root of the thread exceeds that of the 
cross section of the cylindrical body of the bolt a further com- 
plication enters. 

This complication is not limited to malleable castings, but 
is common to all structural materials. Nevertheless, it is not 



300 



American Malleable Cast Iron 



infrequently overlooked. Tensile properties are measured on 
test specimens usually cylindrical, but at any rate of as nearly 
uniform cross section as can be produced. So measured, they do 
accurately define the material. However, if the form of the 
actual structural detail is such that the area of minimum cross 
section is decidedly less than the maximum and is localized in a 
relatively short portion of the axial length of the detail, the 




Fig. 145 V groove in bar 



loading conditions are not comparable to those obtaining in the 
testing ma/chine. 

Thus if a cylindrical bar has a sharp V groove turned into 
it as illustrated in Fig. 145, fracture will take place in the area at 
the root of the groove. However, there will be no significant 
elongation of the piece as a whole, for if the total carrying 
capacity of the section at A- A at the smallest part of the 
bar is not such that when distributed over the area 
of the body of the bair at B, an intensity of loading 
above the yfeld point is obtained, the piece will tear apart at A-A 
without any deformation to each -side of the groove. Even if 
the area A-A is sufficiently near that at B so that the body 
is stressed beyond the yield point the intensity of stress at B 
must be less than in A-A and an inspection of the stress strain 
diagram will show the localization of stretch to be expected due 



Tensile Properties 



301 



to the rapid increase in rate of deformation at the higher stress 
intensities. 

Furthermore the minimum area of cross section apparently 
receives some support from the much larger areas immediatel} r 
adjacent. The net result of both phenomena is that a grooved 
specimen shows an abnormally low elongation and high strength, 
as calculated on the basis of the area of fracture. 




1 



Fig. 146 Necked specimens of pure iron (left) and malleable (right) 

This condition exists in all bolts in which the thread is not 
cut on an upset end. The magnitude of the departure from the 
results wihich would be expected from tension tests is shown in 
the following comparison. Pairs of malleable test specimens of 
the American Society for Testing Materials taken from each of 
six heats were annealed together. One specimen of each pair 
was broken, the other had a sharp V thread turned into it, 20 
threads per one inch, to produce a diameter at the root of the 
thread of 0.505 inch. These specimens were then broken, the 
elongation being measured in the threaded portion of the bar. 



302 American Malleable Cast Iron 

The standard specimens showed a tensile strength of 52,080 
pounds per square inch and an elongation of 15 per cent, and the 
threaded specimens a strength of 60,130 pounds per square inch 
and an elongation of 6^2 per cent. Therefore, in the design of 
threaded members a calculation based on the normal ultimate 
strength distributed over the area at the root of a thread will 
give very safe results. Such threaded details, however, will not 
elongate and inferentially will have their resistance to longitu- 
dinal dynamic tension loads much reduced. 



XVI 

COMPRESSION, CROSS BENDING AND SHEAR 

COMPRESSION is exactly the reverse of tension and is 
a stress often applied to malleable cast iron. In the 
absence of free carbon, in products such as steel and 
wrought iron, the elastic properties in compression are very 
nearly the same as those in tension. In cast iron the resistance 
to compression is considerably higher than that to tension, as 
may be expected from the fact that the graphite flakes com- 
pletely enclosed in iron are less harmful under compression loads 
than under tension. 

Difficulty With Ductile Metals 

Ordinary cast iron specimens fail in compression by shatter- 
ing into fragments, usually with but little bulging at the 
center. It therefore is possible to determine definitely the ulti- 
mate strength of a given specimen. The ductile metals, soft 
steel for instance, are not so definite in their behavior. Instead 
of reaching a load where they fail completely by shearing on 
planes at 45 degrees to the direction of applied stress or by 
rupturing into fragments and ceasing to sustain any load, these 
ductile metals merely flow as the load is applied and never reach 
a point of complete rupture. Thus a cylindrical specimen of 
steel takes a barrel-shaped form, increasing in diameter and de- 
creasing in length. The increased diameter reduces the in- 
tensity of the applied stress and more load therefore can be 
applied. No actual point of failure can be established, but there 
is a limit beyond which distortion of a commercial detail would 
be equivalent to failure. 

Malleable least iron, being capable of .great plastic deforma- 
tion, behaves in this manner under compression, as indicated in 
the two stress strain diagrams in Fig. 147. Curve B in this dia- 
gram indicates the behavior of the same material but not the 



304 



American Malleable Cast Iron 



same specimen from which the diagram, Fig. 142, was charted. 

It will be seen that no definite point of failure can be found 

up to a load of 90,000 pounds per square inch. The permissible 



100 000 
80000 

f 

If, 60 000 

f 

* 

1 

cMOOOO 

i 

i/j 

'E 

o 

20000 


Curve AJ ( 

Curve B: 




12000 
10000 ^ 

3 
O 

c 

I* 

8000 b 
a. 



8 



i/5 
6000 | 

4000 


















7 


_ 


Specimen 
A: 

Diameteri-** 
Height: /" 








^x 


'^ o 


f 




x 


^ 


X 


7 










/ 


X 






/ 








/ 


Mod 
E-? 


u/usoft 
2000001. 


'lastich 
llb.persq 


y J 

in. 7 


o 






/ 










/ 






/ 


f 








i 


f 

D 






/ 










J 


Specimen 

B: 

Area Bsq.in, 
Height: 1334 in. 




I 








/ 


f 




1 








/ 










) 0.04 0.08 0.12 0.16 
0.0004 0.0006 0.000ft 
Unit Compression. 



Fig. 147 Stress 'Strain diagram of malleable cast iron in compression. 

The apparent deflection of 0.00043 at load, Curve B, represents lost 

motion in the machine. 

intensity of compressive stress depends therefore on the per- 
manent set which can be tolerated. The graph readily permits 
of the selection of the load corresponding to any assumed con- 
dition of this kind. Note the general similarity of the elastic 
constants in tension and compression. The proportional limit is 
15,000 pounds per square inch in tension and somewhere above 
13,000 pounds per square inch in compression. The modulus of 
elasticity in tension is 25,000,000 pounds per square inch as 



Compression, Cross Bending and Shear 



305 



compared with 22,000,000 pounds per square inch in (compres- 
sion. Therefore the material behaves in a manner very similar 
to soft steel under the two systems of loading. 

Stresses More Complex 

The foregoing applies only to pure compression loads, 
which exists only in specimens in which the height is not much 
greater than the diameter. In longer columns it is practically 
impossible to keep the axis of the specimen exactly in line with 
the direction of load; the column springs out of line and the 
stresses become more complex. Tests on columns with fixed 
ends 5/8-inch in diameter and 10.6 inches high indicated that up 
to the proportional limit the modulus of elastidty is about 



I! 




Fig. 148 Malleable (center) and cast iron (right) in compression. 

Each specimen before testing was of the size and shape 

shown at the left 



16,000,000 pounds per square inch. The fact that this figure is 
materially less than that obtained in pure compression would 
seem to indicate that even below the proportional limit the stress 
is not a purely concentric compressive one. ' In this column a 
very definite failure at 30,000 pounds per square inch was ob- 
served. 

Stresses in Columns 

The yield point is quite definitely marked at 25,000 pounds 
per square inch. Insufficient data are at hand to warrant the 
definite acceptance of any special column formula for malleable 
cast iron. The columns tested have a ratio of length to diam- 
eter of about 17 and therefore are more slender than the average 
column in actual usf Hence calculations based on an ultimate 



306 American Malleable Cast Iron 

strength of 25,000 pounds per square inch for strut details 
should be amply safe. 

A well known formula for cast iron columns with safety 
factor of 6 is: 

13,333 x area of column 

Safe load= 

(column length) 2 



266 x (diameter of column)* 

This formula is equivalent to the statement that the ultimate 
strength for cast iron columns is equal to 

80,000 pounds per square inch 



i U* ' 



1 + 
266 

The ultimate strength of the malleable columns tested was 
30,000 pounds per square inch, the ratio L/D being 17. If a 
malleable column is subject to the same general laws as a gray 
iron column then to conform to the observed conditions the ulti- 
mate strength of a malleable column will be 
62,000 pounds per square inch 



LV 



266 [D 

This formula applied to the specimens tested in pure com- 
pression would give a breaking load of nearly 62,000 pounds per 
square inch at which figure the material was still carrying load 
but had badly deformed. 

On the basis of a safety factor of 6 on which the formulas 
were, developed the safe crushing strength of malleable comes 
out 10,300 pounds per square inch, which is well below the 
proportional limit. 

It is the writer's opinion that the foregoing formula can be 
safely used as a basis of design. The safety factor could 
probably be reduced readily to 5 and possibly to 4 without 
serious risk. For hollow cylinders Kidder uses the value 1-400 
instead of 1-266 in the above formula; 1-500 for a rectangle 
and 1-135 for an equal armed cross. In any case D is the least 
diameter of the column section. 



Compression, Cross Bending and Shear 307 

When the material is used in the form of a beam, it is sub- 
ject to cross bending stresses. This type of loading is very 
common in practice and is readily reproduced in a testing 
machine. The specifications of the American Society for Test- 
ing Materials before 1918 and of the United States railway 
administration provided for cross bending test results about 
equivalent to a modulus of rupture or apparent maximum fiber 
stress of 64,000 pounds per square inch. This value is decidedly 
too low to correspond to the required tensile strength. The 
modulus of rupture seems to be about twice the ultimate tensile 
strength of the product, the proportional limit corresponding 
to a fiber stress about equal to the ultimate strength in tension. 
While not absolutely exact quantitatively, the foregoing state- 
ments do express the general relationship. Thus a specimen 
cast from metal having a tensile strength of about 51,000 pounds 
per square inch, showed a proportional limit of 50,500 pounds 
per square inch, a yield point of 72,000 pounds per square inch 
and a modulus of rupture of 113,000 pounds per square inch. 
The specimen was rectangular in cross section, ^-inch deep, 1 
inch wide and 12 inches long between supports. The constants 
on specimens of different form might be somewhat different. 

Stresses in Cross Bending 

It is interesting to discuss why the modulus of rupture can 
be higher than either the tensile or compression strength of 
the material. When a specimen is bent there is a tendency to 
compress the material on one side and to stretch it on the other. 
Somewhere between there is a so-called neutral axis where there 
is no change of length. In material in which the elastic be- 
havior in tension and compression is the same the neutral axis 
is midway across the section. The surface fibers of the speci- 
men are strained most under such a condition, the compression 
or stretch decreasing uniformly as the neutral axis is approached. 
As long as the material is perfectly elastic the intensity of stress, 
being proportional to intensity of strain, also varies uniformly 
each way from the neutral axis. Accordingly the material be- 
haves as a perfectly elastic body as long as the outer fiber is not 
loaded beyond the proportional limit. However, after that load- 
ing is passed part of the specimen is subject to plastic de- 



308 



American Malleable Cast Iron 




Fig. 149 Diagram of stresses in cross bending of malleable iron 

formation. The intensity of stress then no longer varies uni- 
formly from O at the neutral axis to a maximum at the top and 
bottom of the cross-section, but there is a band of 'considerable 
width next to the upper and lower boundaries of the cross- 
section in which the stress is fairly uniform. It is only below 
this area, where the stress is below the proportional limit, 
that the uniform decrease is observed. 

The stress in the outer fibers is then not so great as would 
be calculated, since the permanent deformation of the specimen 
has transmitted some of the stress from the outer fiber to those 
further in. Therefore the modulus of rupture is a purely the- 
oretical value not corresponding to any stress actually occurring 
in the specimen. It is merely the extreme fiber stress which 
would be produced at the breaking load if the material be- 
haved as an elastic solid up to the breaking point. 

In Fig. 149 the stresses in a beam are indicated in diagra- 
inatic form. In a beam of depth xx; having its neutral axis O , 
compression stress is measured to the right from xx and tension 
to the left. The proportional limit assumed to be the same 



Compression, Cross Bending and Shear 309 

under either stress is shown by y and 3,'. Loads which do not 
stress the beam above the proportional limit produce a distribii" 
tion of stresses within the beam as shown byAOA. If the load 
is sufficient to produce plastic deformation the stresses may be 
as indicated by Bbob'B' , which is straight only between b and 
b r . If OC is drawn so that the area XOC equals the area 
ObB, the C marks the modulus of rupture if Bbob'B' corres- 
ponds to the load when failure occurs. 

Value Unexpectedly High 

In the cross-bending tests a load of 700 pounds at the 
center of a 12-inch span produced in a l /2 x 1-inch beam a de- 
flection of 0.076 inch at the proportional limit. Up to this 
point the deflection of the beam has been elastic, hence tlie 
value of the modulus of elasticity can be readily calculated. 

Letting W be the load = 700 pounds 
X deflection at center = .076 inches 

L = span of beam = 12 inches 

b = width of beam = 1 inch 

d = depth of beam = ^ inch 
W L 3 

E= =31,800,000-{-pounds per square inch 
x4bd 3 

The value is unexpectedly high both as compared with fig- 
ures for the tension and compression experiments, and as com- 
pared with the value for steel, which is about 29,000,000 pounds 
per square inch. It is barely possible that the error is due 
to slight errors in the uniformity of d in the above formula. 
Furthermore the proportional limit and cognate elastic constants 
are . necessarily somewhat obscured in a beam specimen owing 
to the fact that a relatively small portion only of the beam is 
subjected to maximum stress. Only metal near the surface and 
in the plane of maximum bending moment actually is sub- 
jected to maximum strain, hence the observations are largely 
influenced by the behavior of the much larger mass of metal 
subjected to a much lower intensity of stress. It is probable 
therefore that the elastic constants will be apparently too high 
in specimens of. such form that a considerable amount of material 
is located close to the neutral axis. The departure of the ap- 
parent elastic properties in cross bending from those determined 



310 American Malleable Cast Iron 

in tension will be greater the greater the ratio of the area of 
cross section of the beam to its moment of inertia of that area 
about the neutral axis. For purposes of calculation a conserva- 
tive value probably would be below 29,000,000 and possibly as 
low as 25,000,000 pounds per square inch to conform to the 
tensile results for the modulus of elasticity. 

Shear and Torsion 

Shear and torsion are the two remaining static stresses to 
be considered. They are closely related with one another and 





Disp/Qcemenf of P/anes 
by Tors/onal Shear. 



D/'sp/Qcemeni- of P/anes 
by L/near Shear 



Fig. 150 Displacement of planes by linear shear and (at right) by 

torsional shear 

involve the sliding of the metal on itself, the slip taking place 
along a series of planes within the material. Shear involves a 
linear diplacement, while in torsion the displacement is angu- 
lar. Rivets, bolts or pins are subject to shear when an attempt 
is made to slide the parts they hold together in a direction at 
right angles to the axis of the pin. It also is the shearing 
strength of a material which resists the punching or cutting 
in a die in a pun'ch press. A knowledge of the shearing strength 
of malleable therefore is important both in the design of the 
shackle pins and similar details and in the selection of punch 
presses to be used in fabricating the product. Determinations 
made by driving a punch of known diameter through a plate 
of known thickness and measuring the force exerted in a testing 



Compression, Cross Bending and Shear 



311 



machine have shown the shearing strength of malleable to be 
about 45,000 pounds per square inch. Similar experiments made 
by shearing off a cylindrical pin (double shear) gave values on 
the same metal of a little more than 41,000 pounds per square 



28000 






Yield Point Z3000to.persq.in. 



Proportional Limit 
14000 Ib.persq. in. 



Specimens; 

Diameter --O."90 
Gage Length 5" 




0.002 



0.004- 0.006 O.OOS 0.010 0.012 0.014 
Unit Shearing Strain in Extreme Fiber. 



Fig. 151 Stress strain diagram of malleable cast iron in torsion 

inch. The first mentioned experiments probably are the more 
trustworthy. The experiments were made on metal having a 
probable tensile strength of 50,000 to 52,000 pounds per square 
inch. Therefore the shearing strength apparently is about 15 or 
20 per cent less than the tensile strength of the product. 

In the case of elements in a design subject to twisting loads 
there is a tendency to shear not by a sliding motion of the 
planes within a solid but by a rotating a'ction, one plane over 



312 



American Malleable Cast Iron 



another as shown in Fig. 150. Evidently the action is of exactly 
the same character in both cases. A twisting load is measured 
by the product of the force applied and its distance from the 
axis of rotation. This product is called the moment -of the 
force about the axis of rotation, or more briefly the torque, and 
is measured usually in inch pounds. An inch pound is the 
moment of a force of one pound applied one inch from the 




Fig. 152 Diagram showing factors to be considered in determining 

torsion stresses 

axis of the specimen. When a shaft is twisted the metal is 
evidently deformed or strained more at the surface than at the 
center, the strain being proportional to the distance from the 
axis. As long as the metal obeys Hook's law of the propor- 
tionality of stress to strain that is, as long as it is not stressed 
beyond the proportional limit the stress also is proportional to 
the distance from the tenter and mathematical analysis will de- 
fine the moment of torsional resistance of a section of given 
geometric form in terms of the dimensions of the cross section 
and of the shearing stress in the outside fiber. 

The condition is similar in character to that existing under 
cross-bending stresses. When the intensity of stress in the 
outside fiber passes the proportional limit a mathematical analysis 
of the load condition is no longer possible, since the distribu- 



Compression, Cross Bending and Shear 313 

tion of stress is no longer proportional to the distribution of 
strain. The modulus of rupture in shear or the apparent stress 
in the extreme fiber when breaking occurs is higher than the 
true value, since these layers stressed above the proportional 
limit carry a stress more nearly equal than their distance from 
the axis of rotation would indicate. 

Fig. 151 shows a stress strain diagram of the behavior of the 
material in torsion. The load is recorded in terms of intensity 
of shearing stress in pounds per square inch. This is calculated 
from the known dimensions of the specimen and the measured 
torque. The intensity of shearing strain is determined in terms 
of the ratio of the linear displacement of a point on the surface 
to the gage length. If within a gage length of 5 inches a given 
load has produced a twist such that a point on the surface has 
advanced .07 inch the shearing strain is .07/5=.014. In other 
words, the intensity of shearing strain is measured by the tangent 
of the angle * through which an originally straight element of 
the cylindrical surface is displaced. Thus in Fig. 151, if W is the 
load and D its distance from the center, the torque is WB. 
S is the stress in the outer fiber, L the gage length of the 
specimen, F in linear measure is the displacement of the point 
by twisting under the torque WD from its original position, A 
to A'. The intensity of the shearing strain is F/L, the value of F 
being determined from the known radius of the specimen R 
and the angle e , through which one end of the gage length 
has been twisted with respe'ct to the other. 

R 

e (in radians) being 
F 



if e is in degrees. The value of S is computed from the couple 
WD and the moment of inertia of the circle of radius R about 
its center on the supposition that the stress increases uniformly 
from the center to circumference, 

2WD 
this giving S== -- . 

TR 3 

It will be seen from Fig. 151 that the proportional limits and 



314 American Malleable Cast Iron 

yield points are not very different from those in tension and 
compression. The shearing modulus of elasticity, however, is 
not the same as Young's modulus. The course of the curve 
during plastic deformation is riot very instructive, since it is 
considerably influenced by the testing speed. The preceding dis- 
cussion summarizes the available information with regard to 
the resistance of malleable cast iron to the various well known 
forms of static loading. 



XVII 

FATIGUE, IMPACT, HARDNESS AND WEAR 

THUS far only static loads have been considered in the 
discussion of the mechanical properties of malleable cast 
iron. There are many industrial applications of castings 
in which the structural detail, instead of merely sustaining a 
steady load of some specific character, is subjected to blows, 
shock, or repeated reversals of the applied stress. Unfortunate- 
ly, our knowledge of the principles underlying the behavior of a 
material under dynamic stress still is imperfect. A great deal 
of experimental work of this character has been done and the 
results published but no method is as yet available for systema- 
tically correlating the data and deriving general principles. 

In general the energy of rupture of a given specimen and 
material can be calculated from its stress strain diagram, the 
area below the graph representing the product of stress and 
strain measuring the energy, in foot pounds, for example. The 
specimen may absorb this amount of kinetic energy from an im- 
pact or other dynamic stress. This however, does not tell the 
entire story for the possibility of a time factor enters. Assume 
that the impact is due to a weight moving with a given velocity. 
The specimen absorbs energy from the weight by retarding, and 
ultimately stopping its motion. Energy is measured as a prod- 
uct of mass and therefore acceleration in the energy absorbed 
by the specimen is measured by the product of the mass of 
the weight and its (negative) acceleration when being stopped 
by the weight. If we have means of knowing the maximum 
rate of retardation while the weight is being stopped, we 

M 

can calculate the maximum stress as being and where M 

G 

is the mass of the hammer; A, its maximum retardation and 
G, the acceleration due to gravity. Obviously this value cannot 
be greater than the ultimate strength of the specimen without 
producing failure. 



316 American Malleable Cast Iron 

Dynamic Stresses in Two Groups 

Two groups of dynamic stresses may be recognized. 
One of these results from impact or blows.' In general such 
stresses are in one direction only and usually are of considerable 
intensity. They may be applied axially, either in tension or com- 
pression to 'the detail involved, or may be applied to a cantilever 
beam or to one supported at both ends. Occasionally the load- 
ing is even more complex. 

The other group of stresses results from repeated, usually 
rapid, reversals of stress, sometimes of small magnitude, and 
usually through an extended period of time. The stresses in a 
rotating shaft acting also as a beam are of this character, as 
are also the stresses in the leaves of an automobile spring, 
those in the couplers of a train while in motion, and those 
resulting from vibration. 

In the former group a mathematical analysis of the service 
conditions is almost impossible. The material usually is stressed 
beyond its elastic limit by each blow so that it is impossible 
to determine the stress distribution within the metal. The energy 
absorbed by a given specimen before breaking is frequently 
less if the energy be delivered by a single impact than if deliv- 
ered by a series of equal smaller impacts whose 
sum is equal to the energy of the single impact required 
for fracture. If fracture takes place under a series of 
blows the energy absorbed depends on whether the successive 
blows are of the same intensity or increase in intensity with 
each succeeding blow. The subject will be discussed more fully 
in the next chapter. 

Thus it is seen that practically no two cases are alike 
in practice and that the problem is so complex as to prevent 
generalization from the results of different groups of tests by 
mathematical analysis. 

Therefore it is impossible to furnish quantitative data 
to be used as a basis of computation for mechanical details 
subject .to impact. 

The comparison of the behavior of several materials under 
impact is easier since the tests of all can be made under the 
same circumstances and on geometrically similar specimens. 



Fatigue, Impact Hardness and Wear 317 

To avoid the complication resulting from -the cumulative effect 
of repeated stresses each insufficient to produce failure, the 
experiment usually is designed to break the specimen at the 
first blow and to measure the energy absorbed in breaking by 
taking the difference in -the kinetic energy of the system be- 
fore and after failure. The tests so made on various types 
of machines do not give comparable data; the results differ 
with the design of the hammer, the shape of the specimen 
and its manner of support. 

It is said that on the Charpy machine, which takes a speci- 
men 10 millimeters square by 53.3 millimeters long, with a 
45-degree V notch 3 millimeters deep at the center, about 7 l /2 
foot pounds are absorbed in breaking a specimen of normal 
malleable cast iron. On similar specimens except that the notch 
is made by a thin saw cut running into a hole 1 millimeter in 
diameter, 7 l / 2 to 8^2 foot pounds of energy usually produce 
rupture in tests in the author's laboratory. On the Olsen ma- 
chine breaking a round cantilever specimen with a 45-degree V 
notch 0.122 inch deep 1.10 inches from one end and with the 
notch clamped even with the vice jaws holding the specimen and 
the hammer striking 0.625 inch above the notch, the indicated 
energy absorption in breaking is 13 foot pounds. 

Testing Tensile Impact Stresses 

Impact tests may also be made in tension- In such cases 
the test is made on a screw-end tensile piece, one end of which 
screws into the hammer of the Oharpy machine. The other end 
of the specimen carries a yoke which strikes a fixed portion of 
the frame of the machine just as the hammer is at the lowest 
point of its travel. The dimensions are so chosen that the 
energy of the hammer is sufficient to rupture the piece. 

Evidently, for a given material the energy to produce 
rupture varies as the cross sectional area and as the length 
of the specimen. Upon the area depends the resistance of the 
material to tensile loads, and the length is a factor, since ob- 
viously twice as much work is done in stretching a piece two 
inches long a given percentage of its length as in stretching a 
piece one inch long an equal percentage. 



318 American Malleable Cast Iron 

Speaking more technically, the expression for work is 
fs where / is the force exerted and .? is 'the distance through 
which the hammer moves while the specimen is breaking. If 
a is the area of the specimen, E its elongation and / its 
length, and if t is its ultimate tensile strength: 

f = Kta 
s = El 

fs = Kta El = KtEv 

where K is a constant depending upon the form of the stress 
strain diagram and v the volume of the specimen equal to a I. 
The resistance to tensile impact is thus to be expressed 
not in pounds per square inch of section but in foot pounds 
per cubic inch of metal deformed. 

It is noteworthy that while in static tension a defect op- 
erates to reduce the strength rather less than in proportion 
to its area and the elongation considerably, in dynamic test- 
ing practically absolute soundness of specimen is required. If 
a notch or shrink exists sufficiently large to so far reduce 
the area as to localize the stretch wiithiii its own length the 
gage length upon which the work is expended becomes only 
the axial length of the shrink. This may be only 10 per cent or 
even only 1 per cent -of the apparent gage length and the foot 
pounds absorbed if calculated on the intended gage length 
would be only 10 or 1 per cent, respectively, of the correct 
values. Care must further be used to see that the specimen 
increases in size immediately beyond the gage length. Any 
stretch outside the gage length erroneously credits additional 
energy to the specimen. 

Sound specimens of good malleable iron 0.1 square inch 
in area and 2 inches long showed results as follows when 
tested : 

Energy df rupture Elongation 

(foot pounds iper (per cent an 

cubic inidh) 2 imdh-es) 

755 15 

640 

999 20 

930 

The relation between resistance to dynamic tension and 
elongation is plainly 'Shown and is still more plainly visible 



Fatigue, Impact Hardness and Wear 



319 



by examining -the following tests on good malleable containing 
small shrinks. 



Energy of iruiptuire 

(ifioiolt (pounds per 

icu'bic indh) 

102 

115 

345 



Elongation 

(per 'cent in 

2 inic'hes) 



The graph in Fig. 153 which summarizes these data indicates 
the almost direct proportionality of elongation and resistance 
to tensile impact even when the former is artificially affected 
by mechanical defects. 



1000 

900 

JC 
OflflO 










































^^ 


* 








































^ 






































.* 


^ 










c ouo 

o700 
"S 

3 

k m 

tnAQO 

l m 



^ZOQ 
100 






























; 


^ 






































.* 


^ 


^~ 






































S 


^ 






































^ 


^ 






































^ 








































^ 


s* 






































^ 


^ 






































* 


^ 








































5 t 


3 10 15 20 

Per Cent Elonqation 



Fig. 153. Effect of elongation of specimen on the resistance to dynamic 

tensile loads 



The presence of temper carbon nodules operates just like 
any other mechanical discontinuity. Accordingly it is almost im- 
possible to obtain consistent results in tensile impact from mal- 
leable. All the results doubtless are lower than the correct value 
and since they are far from concordant their practical interpre- 
tation is doubtful. At best the test is poorly suited to so hetero- 
geneous a material. 

From 'the energy of rupture, the measured elongation and 
the known dimensions of the specimen we can calculate a 
modulus of rupture as the average intensity of tensile stress in 
pounds per square inch developed during rupture of the ma- 
terial. Disregarding the very small elastic deformation which 



320 American Malleable Cast Iron 

has disappeared when the permanent elongation is measured 
we can proceed in the light of the previous formulas to solve 
the equation: 

fs = KtEv 

for K t, the modulus of rupture. The values of js, corre- 
sponding to given value of /, are shown in the preceding tables 
on the basis of v being unity. 

The average value of Kt on the four sound specimens 
previously quoted was 58,600 pounds per square inch, the three 
imperfect ones showing in order 3500, 4700, and 5500 pounds 
per square inch. 

Unfortunately the static tensile properties of the material 
were not actually determined. From the stress strain curve 
shown in Fig. 139 in Chapter XV, we may derive an 
approximation of the value of K. The average abscissa (stress 
ordinate) of that graph is about 0.88 times the stress 
art rupture. Using K as 0.14 we can calculate t in the ex- 
pression 

Kt 58,600 pounds per square inch 

with the result that t has an approximate value of 66,600 
pounds per square inch. 

While the data are both too few and too inaccurate for 
definite conclusion there is a presumption at least that in ten- 
sion the material fails under impact at materially higher stresses 
than under static loads but that the elongation is not greatly 
different in the two conditions. 

The effect of velocity of impact on maximum stress is 
among the most interesting but least understood phenomena 
in the utilization of materials. It is hoped that work in pre- 
paration under the author's direction will be productive of 
more accurate and useful conclusions. 

A number of tests have been devised in which repeated 
impact is applied. Such tests must be closely standardized 
as to the form of specimen and the energy of the blow. The 
amount by which the stresses set up by a single blow exceed 
the yield point greatly affects the results of the tests. 
Any variable in design or material which affects the yield point 



Fatigue, Impact Hardness and Wear 



321 



of the specimen as a whole therefore profoundly alters the re- 
sult of such a test. 

A dynamic test developed especially for application to mal- 
leable iron was devised at the general suggestion of the late B. 
J. Walker and is sometimes known by his name. In this test 
a wedge specimen 6 inches long by 1 inch wide, tapering from 
J /2 to 1-16 'inch thick is used. The specimen is set on its 
thicker end on the anvil of a drop hammer and subjected to 





Fig. 154. Walker test wedges 

blows of 70 foot pounds. The first blow is struck straight 
down on the point of the wedge, curling it over, and for each 
succeeding blow the specimen must be held so that 
the point which will be struck by the hammer is 
directly over the point of support. This is a difficult 
requirement to fulfill and the test, while measuring a very 
useful property, is almost incapable of quantitative reproduc- 
tion and is accordingly of only slight interest to the consumer. 

A normal malleable is supposed to survive 20 blows (ag- 
gregating 1400 foot pounds) in this test and to break not 
more than 1% inches from the thick end of the wedge. A 
better mechanical execution of this test possibly would yield 



322 



American Malleable Cast Iron 




Fig. 155. Behavior of malleable iron under fatigue as a rotating beam 

results of value and has been studied by the writer for some 
time. 

The writer has been informed that tests by the Humphrey 
static notched bar method yield valuable data as to brittleness 
but has not personally investigated the matter. 

Tests can readily be made under dynamic stresses of the 
second type, involving repeated reversals of direction under 
rather small loads. Machines of the Upton Lewis type, 
especially when equipped for alternate torsion, are valuable for 
this purpose, particularly when considerable intensity of stress 
is desired. Machines of the Wohler, Whiter Souther, or Far- 
mer-type apply well to the repetition of smaller stresses existing 
in rotating specimens subjected to bending. 

W. W. Flagle in the author's laboratory has determined the 
relation between maximum fiber stress and life of a typical 
malleable, using the Farmer-type machine. The results of his 
investigation are shown in Fig. 155 in which life is plotted 
against stress to a logarithmic scale as suggested by Moore. It 
will be seen that the fatigue or endurance limit of malleable is at 
25,000 pounds per square inch. Malleable will resist alterations 
of stress of this magnitude indefinitely certainly hundreds of 
millions of times. Reference should be made to Moore's data 
for similar information on a variety of rolled products. 

Prof. H. F. Moore is quoted to the effect that ingot iron 
(ferrite) will withstand 100,000,000 repetitions of a stress 1.6 
times its proportional limit, as determined in tension. This 
would indicate the probable great endurance of the matrix 
of malleable. 



Fatigue, Impact Hardness and Wear 



323 



It will be seen that much remains to 'be done in the quan- 
titative investigation of the resistance of malleable to fatigue 
and to impact. Fortunately, qualitative information of this 
character is readily accessible in view of the long continued 
application of malleable iron in the industrial arts. The prac- 
tical experience which attracted consumers to this product 
when searching for a 'shock resisting material and in a period 
when methods of tests and metallography were practically un- 
known seems to have been well founded. 

A logical reason now is available for this quality. Being 
largely ferrite, malleable is soft and ductile, as are all other 
materials in which ferrite predominates. Wrought iron is a 
conspicuous example of such materials; malleable is not as 
ductile as wrought iron because of the temper carbon present. 
Its resistance to deformation and shock, however, depend upon 
this principle. 

Malleable lias a further great advantage over many other 
materials in that the temper carbon granules, while of a form 
to affect the physical properties only to a relatively slight ex- 




Fig. 156. Separation of grains by repeated cross bendings 



324 American Malleable Cast Iron 

tent, operate as a hindrance to failure under alternating stresses 
by fatigue. Such failures frequently occur by the penetration 
of a crack 'between adjacent grains of the metal. When such 
a crack begins to form in malleable it does not penetrate 
far before it strikes one or more carbon granules. These 
stop its further progress just as a hole drilled at the end of 
a crack in a bell prevents the growth of the crack. 

The best evidence available as to the shock resisting quali- 
ties of the material are derived from the years of service which 
properly made malleable, has given in draft gears, rail anchors, 
automobile hubs and spring brackets, car couplers (until high 
train loads forced the 'adoption of a material capable of higher 
unit stresses), and an indefiniite number of similar applications. 

For some kinds of service the fitness of a material for the 
use intended may depend not so much upon its strength under 
load as upon its machineability, resistance to abrasion, co- 
efficient of friction and similar properties. 

The property which enables a material to resist cutting or 
wear is somewhat loosely called hardness. Unfortunately 
this term is not clearly defined and often it is misinterpreted. 
Moreover, the commercial methods for measuring hardness in 
metals actually measure resistance to penetration under defined 
conditions' a property bearing no practical or theoretical rela- 
tion to hardness as understood in 'the definition given above. 

Two methods of measuring so called hardness a'fe in com- 
mon use- In Brinell's method, hardness is determined by the 
depth to which a 10-millimeter ball will penetrate under a 
load of 3000 kilograms. In Shore's method, the rebound of a 
hammer falling from a fixed height measures, in effect, the 
work absorbed by the plastic deformation of the material un- 
der a standard load. The results of the Brinell test bear 
a fairly close relationship to the ultimate strength of the 
material, while the data obtained by the Shore method should 
conform to the elastic limit. 

The Brinell number of normal malleable cast iron is from 
about 101 to 145 and increases as does the tensile strength 
with decreasing carbon. Common values are around 110-120. 
Fig. 157 shows the relation between the Brinell number and 



Fatigue, Impact Hardness and Wear 



325 



the strength of a wide range of malleable iron. The heavy 
line indicates the probable relationship and the shaded area the 
limits of variation from the probable value. The scleroscope 
number is somewhat erratic, running from about 15 to about 20. 
The Shore nurriber actually is surprisingly constant in 
malleable of quite variable tensile properties. Some experi- 
mental data as to the relation between this hardness number 



I 

^120 

QJ 



100 



v 7 * W 



YA M 



& 



Waximum_ 7//A 



*-\ 



A 



Y/* 



in/'tftum 



t 



**? 







36 38 4O 42 44- 46 46 5O 52 54 S 53 O 



Fig. 157. Relation between Brinell number and strength of malleable iron 

specimens 

and the Brinell number are presented in Fig. 158. The explana- 
tion of the approximate constancy of the Shore number is as 
follows : 

The variation in physical properties of malleable are due 
primarily to the ratio of ferrite to temper carbon and not to 
variations 'in -the properties of the ferrite. The Shore test 
being made on an almost microscopic area determines only the 
properties of the ferrite. If by accident a temper carbon 
grain is struck no rebound at all is observed- The composition 
of the ferrite is not sufficiently variable to alter its physical 
properties. 



326 



American Malleable Cast Iron 



Neither of -the hardness numbers bears any particular re- 
lation to completeness of anneal. White iron is harder than 
malleable so that the effect of annealing is to soften the metal 
under both tests. Under commercial conditions, however, an- 
nealing is almost never so far from complete that this fact 
is of any value in inspecting material. Malleable castings which 
are sufficiently annealed to pass any ordinary inspection usually 



/v* 



/7 



/* 



/4 



W- 



tf/'/sy^'// M&s-t/sy&^s 



Fig. \*&. Graph showing comparison of Brinell and Shore numbers 
indicating relation between them is not definite 

contain only very small amounts of ungraphitized carbides. The 
remaining combined carbon is either found as cementite in very 
minute grains scattered throughout the castings or as a thin 
layer of pearlite just under the surface. 

The former condition would have no effect on the Brinell 
hardness and would affect the scleroscope hardness only if 
the hammer struck such a grain by accident. The thin sheet 
of pearlite does not increase the <,Brinell hardness appreciably, 
since the pearlite layer is merely crushed down upon the deeper 
material which is soft. The Shore number may be affected by 



Fatigue, Impact Hardness and Wear 327 

pearl ite if this 'be present at the finished surface of this 
sample and if the layers are heavy enough to absorb the im- 
pact. Neither of these conditions usually exists for the pear- 
lite is originally covered with ferrite and if in producing a 
finished flat surface for test any considerable amount of ma- 
terial is removed the pearlite layer may be completely de- 
stroyed. The point 'has been emphasized by Prof. Touceda 
and also by W. R. Bean. 

Therefore these tests are not directly applicable to the 
commercial valuation of malleable with reference to its cutting 
properties. The important considerations in industrial uses of 
malleable involve cutting hardness which is undesirable in 
fabricating the product in the machine shop, and wearing hard- 
ness or resistance to abrasion, which resists the destruction of 
a bearing or similar detail where subjected to friction. 

These two conditions are different manifestations of near- 
ly the same property. Ease of machining and resistance to 
wear are incompatible with one another. No direct means of 
measuring cutting hardness are known. The hardness of min- 
erals is measured by comparison with an arbitrary scale rang- 
ing from talc, having a 'hardness designated as V to diamond, 
with a hardness of 10. Any given mineral can be rated by 
determining between which two numerals its hardness lies. 
Thus, pyrite, which scratches feldspar, hardness 6, but is 
scratched by quartz, hardness 7, is given an intermediate num- 
ber, in this case 6.3. On this 'scale iron has a hardness 
of about 4 or 5 and steel a hardness of from 5 to 8.5. This 
test besides being very unsensitive can be applied only to the 
extreme surface of a metal. In the case of malleable this 
always is ferrite, which shows a hardness of 4. 

Turner has devised a method based on cutting a line 
into the surface of the material. This is done by pressing the 
V-shaped nose of a diamond against the metal under a def- 
inite pressure. The cross section of the furrow cut, as meas- 
ured by the width of the groove, is intended to be the measure 
of cutting hardness. This method is applicable only to the sur- 
face of an article. Since the surface must be smooth, it is diffi- 
cult to apply this test to malleable containing a pearlite layer, as 



328 American Malleable Cast Iron 

pointed out in the discussion of the Shore hardness. The 
test is not used extensively, and the writer knows of no data 
obtained from its application to malleable iron- 

Similar tests, made by scratching polished samples and 
examining the scratch under the microscope indicate that the 
hardness of the micro-constituent present in normal hard iron 
and malleable iron is in the following order: Ferrite, pearlite, 
cementite. Ferrite is soft and cementite nearly as hard as 
carborundum, as measured by resistance to scratching. 

Study of Cutting of Metals 

The principles underlying the machining of metals have 
been investigated by a number of experimenters, notably, Nich- 
olson, Frederick Taylor and Herbert. The special case of 
machining by twist drills has been still more fully investi- 
gated for example, in the engineering experiment station of 
the University of Illinios. 

While these studies have thrown much light upon the prin- 
ciples underlying the cutting of metals and liave served in 
some cases, notably in Herbert's experiments, to test the qual- 
ity of cutting tools, they were not generally conducted so as 
to develop any technique for the testing of a material for 
machineability. Accordingly, no method is yet available for 
determining how readily an existing structural detail can be 
machined. Therefore it is not surprising that there are no 
means for quantitatively comparing the machining properties 
of malleable cast iron with those of similar materials. 

However the fundamental relationships involved are eas- 
ily summarized. To the consumer, machineability means the 
removal of the required amount of metal in the minimum 
of time and with the minlimium of tool destruction. Many 
investigations have approached the subject by measuring the 
load on the nose of the lathe tool. Nicholson measured this 
load parallel to three rectangular co-ordinates radial, tangential, 
and axial with reference to the revolving specimen and used 
only two materials, soft and medium steel. His work resulted 
in a mass of data concerning the relation between the cutting 
angles of the tool and the direction and magnitude of the 



Fatigue, Impact Hardness and Wear 329 

resultant forces. He also made a limited number of tests 
on *he effect of cutting angles on tool life. 

For 'the present purpose his work may be summarized as 
having demonstrated that the tangential thrust on the tool 
is independent of the cutting speed and that the life of the 
tool increases as the cutting angle increases. Taylor in his 
monumental monograph "The Art of Cutting Metals," covered 
exhaustive investigations on feeds, depth of cut, form of tool, 
cutting speed load on the tool point and tool life. He deduced 
the fact that the load on the tool point is dependent only 
on the area of the chip being removed and the material 
being cut and independent of the cutting speed, form of tool, 
relation between depth of cut and feed, or any other varia- 
ble. 

This seems to indicate that the load on the tool point 
per unit area of cut is a constant, readily determined for a 
given material. This is true, 'but unfortunately the deter- 
mination of this constant has no practical use since Taylor 
also proved conclusively that no determinable relationship ex- 
ists between this constant and tool wear or economical cut- 
ting speed. 

Herbert has shown from Taylor's data that tool failure re- 
sults from the heat evolved in cutting and has deduced a for- 
mula for determining the relation between the tool temperature 
and feed, cut, and speed. He also has proved that the most 
economical tool service corresponds to a definite tempera- 
ture which is a function of the tool steel used. 

From this it will foe seen that all of the work pre- 
viously done has not resulted in conclusions applicable to the 
defining of the machineability of a given material in terms 
of permissible cutting speeds. 

Consumer Wants Cutting Speed 

In general the consumer is not interested in the load at 
the tool point, since he is quite willing to adopt machine and 
tool designs capable of sustaining any loads which may be 
developed, providing only -he is informed as to the probable 
stress to be encountered. The power consumed in removing 



330 



American Malleable Cast Iron 



the material also is of little interest, since this is not a major 
item of expense and can be met by the installation of a suffi- 
ciently heavy drive. His chief requirement is a fast cutting 
speed with long tool life. Tool life when determined by nor- 



4QOOO 

<0' 1600 

$1500 
o 
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^ 1400 

'5 1300 

"b 

1200 

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fensi/e Strength in Pounds Per Square Inch. 
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Relation Between L oad on One Inch 
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jqooo 45 y ooo 50.000 
Pounds Per SQuare Inch 



Fig. 159. Tests of machining properties of malleable cast iron 

The curves are plotted from data presented by Edwin K. Smith and 
William Barr, Milwaukee, in a paper prepared for the American Found- 
rymen's association, 1919. 

mal conditions is fixed by the working temperature of the tool, 
determined by cutting conditions and the material being ma- 
chined. Suitable investigation by Herbert's methods should 
yield useful results in the relative rating of different metals, 
but the data are not available. 

Smith and Barr have attempted to determine the relative 



Fatigue, Impact Hardness and Wear 331 

machineability of different samples of malleable and to com- 
pare the data with that for other materials. Their experiments 
were based on the torque required to cut threads into the dif- 
ferent samples with two dies taken as standards and also by 
measuring the penetration per revolution of a standard drill 
under a standard load. 

Unfortunately the data are incapable of conversion into 
absolute figures. Smith and Barr apparently felt that they had 
secured evidence pointing toward the fact that iron high in 
tensile strength is relatively difficult to machine. The author 
does not feel that this conclusion is necessarily justified by the 
observed facts. Fig. 159 shows graphically the results of their in- 
vestigations and in the writer's opinion they indicate that the 
machineability of normal malleable is within the limit of error 
of the data. 

However these investigators have accumulated useful data 
comparing the resistance to drilling of malleable cast iron, gray 
cast iron and steel- Their results indicate that the penetration 
of a drill under standard conditions is at the rate of 0.249 
inch per minute and 0.196 inch per minute in two specimens 
of gray iron; 0.209 to 0.240 inch per minute in 17 samples 
of malleable and 0.052 to 0.085 inch per minute in three 
samples of steel. This proves the general thesis that malleable 
is comparatively easy to machine. 

An exhaustive study of all types of machining operations, 
using the best equipment known, is in progress under the 
writer's direction. In connection with this work, W. W. Flagle 
has gathered data as to the load on twist drills of standard form- 
when drilling fully annealed malleable. 

The investigation included a study of the effect of drill 
diameter, feed, -speed and character of metal being cut. The 
effect of drill form, of lubricants and the life of drills is 
being further investigated. 

The work is far too voluminous for presentation in detail 
in the present connection and is reserved for publication, in 
a more appropriate place. A few of tbe more interesting 
conclusions may be abstracted as follows. 



332 



American Malleable Cast Iron 



The torque on a drill, cutting malleable iron varies as 
the square of the diameter and approximately directly as the 
feed. The thrust varies directly as the feed and approximate- 
ly as 'the drill diameter. The effect of speed on torque and 
thrust is but small for rates from 40 to 640 revolutions 



3/.OW 

30.000 
29.000 
28000 
27000 
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22,000 
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20,000 

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? 200 300 400 $0 600 $25.005 Dl .02 .04 
Sfiee&/s? /&?M. Feed Per tfe\/o/vf/ on 

J/?d- feeds 



Fig. 160. Graph showing values of a in drilling formula 

per minute. Both loads decrease slightly with increasing 

speed and are more nearly constant with variations in speed 
at high speeds than at low. 

Representing by T v the torque and by T t the thrust 

of a drill of diameter d f running at s revolutions per minute 

with a feed, /, in a certain uniform iron 



and 



T t = bfd 



Fatigue, Impact Hardness and Wear 



333 



in which a and b are constants depending on s f t, and d. 
The values of a and b can 'be interpolated from the graphs 
in Fig. 160 and 161 respectively. 

The drilling properties are further affected by variations 
in the character of the metal- The investigation disclosed 



/00,000 



92/XX>\ 



dspoo 

86OO& 

84,00, 

82000 

80&00 

780OO 



76,000 
100 



X 



\\ 



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I I I 



13m 

yoo&W 

W&ffi. 



?00 



400 3W 600 



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a 



J" M 



Fig. 161. Graph showing values of b in drilling formula 

that machining stresses were not related to either Brinell num- 
ber or strength as effect to cause. However, there is a gen- 
eral coincidence between the three properties in completely 
annealed malleable. 

The data of Figs. 160 and 161 were obtained from malle- 
able equivalent to a tensile strength of 52,000 pounds per square 
inch and a Brinell number of 120. In Figs. 162 and 163 the 
effect of Brinell number and strength on T v and T t are plotted 
in the form of coefficients for reducing, the previously calcu- 
lated values to suit other tensile or hardness properties. 



334 



American Malleable Cast Iron 



The observations in a measure substantiate Smith and 
Barr's ideas as to the increased machining difficulty of stronger 
metal. Apparently there is a variation of from 25 to 30 pet- 
cent in the stresses developed as between the weakest and 
strongest malleable. 

These variations are not nearly sufficient to bridge the 
gap between malleable and even the softest steel. 






90 



to 



LX 



Fig. 162. Correction factor for drill torque and thrust in terms of 

ultimate strength 

It is again to be emphasized that neither the author's data 
nor that of Smith and Barr can be interpreted in terms of 
tool life. Furthermore, it must be clearly remembered that the 
data were all obtained on completely graphitized material and 
that nothing heretofore sajid has any relation whatever to white 
edged or white material resulting from mischances in annealing. 
The subject has already been referred to in connection with 



Fatigue, Impact Hardness and Wear 



335 



the discussion of Brinell numbers where it was shown that 
such mischances do not necessarily influence the hardness test. 
They do, however, greatly affect machineability both with re- 
spect to tool life and stresses. 

The machining difficulties occasionally encountered might 
be explained on either of three grounds. First, the material 



/.SO 



{.25 



93 
.90 
.83 
.80 



Fig. 163. Correction factor for drill torque and thrust in terms of 

Brinell number 

may be so tough 'that the heat developed per unit of time causes 
the tool temperature to increase rapidly. The tool fails for per- 
fectly normal causes but under much accelerated conditions. 
Second, the material may contain particles sufficiently hard to 
work as an abrasive and so destroy the cutting edge. Third, 



336 American Malleable Cast Iron 

the material may set up so heavy a tangential load in the 
tool point as to cause it to break off irrespective of the failure 
of the cutting edge. 

A study of abnormally early tool failures seems to indi- 
cate the occurrence of failures of all three types- Since all 
malleable cast iron consists only of ferrite and temper carbon 
it is difficult to see how any great difference could exist between 
different products varying only in the percentage of temper 
carbon present. This is all the more true since in general the 
cutting is in a region where relatively little carbon remains due 
to decarburization in anneal- 

In the case of imperfectly 'annealed iron a condition ac- 
counting fof any or all these causes of failure may exist. 
White cast iron is known to exert very heavy unit stress on the 
tool point, hence a metal so imperfectly annealed as to retain 
much of its original pearlite-cementite dendritic structure would 
set up abnormal tool loads and cause a failure of the third 
class. 

Material in which cooling 'has been so slow that all pearlite 
is graphitized but in which some cementite persists would pro- 
duce failures of the second class. Cementite is an exceedingly 
hard ingredient, the hardest of any carbon-iron alloy. Its hard- 
ness on the mineralogical scale is between 8 and 9, since it 
is harder than the hardest steels. In imperfect malleable of 
this kind it would be found scattered as granules through the 
ferrite. Being present In very small amount only, it could 
hardly exert any very great effect on the ferrite mass in 
which it is imbedded and therefore is not likely to either in- 
crease the tool temperature or the load thereon. The tool edge 
however, will encounter those granules lying in the finished 
surface and these grains will rapidly wear away the cutting 
edge which rubs against them. 

Failures of the first class are very largely due to so 
called "picture frame" iron in which there remains a consider- 
able pearlite layer just under the surface. This layer is identical 
in composition and properties with annealed tool steel. As 
such the cutting speed will not be great before sufficient heat 
is generated to rapidly destroy the tool. Unusually bad cases 



Fatigue, Impact Hardness and Wear 337 

of this character may also produce failures of the third class. 
It should 'be remembered that all normally made malleable 
is easily machined, there being minor differences only between 
the machineability of malleable of varying composition. When 
machining difficulties are encountered the explanation general- 
ly is due to failures of execution in individual cases rather 
than to the character of the product as a whole. 

Resistance to Friction 

To all intents and purposes, resistance to frictional wear 
obviously is the converse of machineability. Experience seems 
to indicate that the most successful bearing metals are those 
consisting of fairly soft matrix in which a relative hard con- 
stituent is imbedded. The hard constituent takes the wear and 
is supported by the soft. Further, the soft constituent wearing 
down a little, furnishes the certainty of a supply of lubricant to 
the bearing. The soft ingredient is further desirable since if a 
grain of abrasive enters the bearing and lodges tightly in 
the bearing metal it will >soon cut away the rotating mem- 
ber where the latter rubs against it. With a soft bearing metal 
the grit will at most cut a groove in the easily replaced bearing 
without damage to the shaft. 

Since malleable does not contain the hard skeleton or 
grain required to promote long life it cannot be regarded as 
suitable metal to resist wear. By 'analogy also with gray iron 
this conclusion seems warranted. Extremely soft gray irons, 
which resemble malleable more closely than those containing 
more combined carbon, are inferior to the harder irons as 
bearing materials. 

Malleable is not a suitable material of construction, where 
the major requirement is resistance to wear, as for instance 
in journal bearing's. 

It will of course resist minor friction incident to other 
service. . Under such circumstances, the conditions as to hard- 
ness and smoothness of the material rubbing against it is of 
prime importance in determining the service to be expected. 
Determinations of the coefficient of friction for the metal are 
not available. While they would be highly interesting, they 



338 American Malleable Cast Iron 

are not of great practical application because of the general 
unsuitability of malleable for friction service and because under 
normal lubricating conditions in machine parts there is not 
metallic contact between shaft and bearing. Therefore the 
friction losses depend mainly upon the lubricant and not 
upon the material of the shaft and its support. 



XVIII 

PLASTIC DEFORMATION 

IN CONSIDERING the behavior of malleable cast iron under 
mechanical stress we have noted that like most other materials 
its deformation, or strain, under load is of two entirely 
distinct characters, depending upon the intensity of the stress. 
Under light loads the deformation is elastic; that is, it is pro- 
portional to the applied stress and is not permanent, the metal 
returning to its original dimensions upon the removal of the load. 
At higher stresses the strain increases very rapidly and the spe- 
cimen becomes permanently deformed. 

This change of form is termed "plastic" deformation as dis- 
tinguished from "elastic," and especially characterizes ductile 
metals. Much interesting work has been done in the investiga- 
tion of the phenomenon of plastic flow, the property by virtue of 
which a material is malleable and ductile. The property is 
usually measured in terms of yield point, reduction in area and 
elongation. 

Nutting has developed the thesis that plastic strain may be 
expressed as the product of constant and exponential functions 
of the stress and time. In other words, the strain is measured 
by the expression AS x t y where S is stress, t time and A, x and -v 
characteristics of the material. Hook's law is a special case of 
this formula when x=\ and y==0. 

The author has no desire, in the present connection, to at- 
tempt any exposition of the theoretical aspects of plastic flow. 
However, since malleable cast iron is in quite a marked degree 
capable of plastic deformation, and in fact, owes many of its 
most valuable properties to this property, it seems well to sum- 
marize the effect of plastic deformation on the metal. 

Summary of Theory 

As has been shown, malleable is in effect a mass of ferrite 
made up of individual grains. Each grain is made up of many 
crystals all oriented in space in the same direction. The several 



340 American Malleable Cast Iron 

grains are held together, according to the now generally accept- 
ed view, by a thin layer of amorphous (non-crystalline) iron 
acting as a cement. This amorphous iron is supposed to be 
stronger than the crystalline variety and is supposed to behave 
like a very viscous liquid. It is also supposed that crystalline 
iron will go over into amorphous iron under heavy stresses. 

The behavior of a metal under even the simplest stresses 
is as a rule complex. Even when a stress is applied in only 
one direction the behavior of the material indicates that com- 
plex systems of forces result. While we speak of the elonga- 
tion or compression of a metal these terms are in a sense mis- 
nomers, since solids are but slightly compressible in the sense 
of a decrease in volume or mutatis mutandis capable of elonga- 
tion. Metals compressed or lengthened by plastic deforma- 
tion do not materially gain or lose bulk. For example a speci- 
men compressed until it was only one-fourth its original height 
had its density reduced from 7.206 to 7.196 in the process, a 
change in the opposite direction to what might be expected. 

Behavior of Specimens 

The increase or decrease of dimensions parallel to the di- 
rection of applied stress is made up by decreases or increases of 
cross section in a plane normal to the axis of stress; the tensile 
specimen necks in, the compression specimen becomes barrel 
shaped. 

We note also that plastic materials do not fail in tension or 
compression in a plane normal to the stress. The tension speci- 
men shows a cup shaped fracture, at least on one side of the 
break. The compression specimen tears apart either in a plane 
approximately at 45 degrees to the direction of stress, or more 
rarely on a conical surface whose axis of symetry coincides with 
the direction of load. 

From these observations it is evident that there is a consid- 
erable motion of translation within the stressed material in di- 
rections at right angles to the direction of the applied stress. 
This rearrangement may conceivably be of two kinds in a ma- 
terial composed of crystalline grains either a deformation of 
the individual grain (intragranular) or a separation and 



Plastic Deformation 341 



rearrangement of the grains at their boundaries (intergranular). 

Both phenomena are easily recognized. A deformation of 

the grain itself is accomplished by a shearing of the grain along 




Fig. 164. Slip bands in ferrite of malleable iron 

Nitric acid etch 1000 diameters 

Note that there is but little evidence of any separation at grain boundaries 

mtragranular crystal boundaries. Such a slip, if occurring in 
a grain in a polished surface, shows a series of parallel lines 
on the polished surfate which are fine grooves and ridges in 
the originally plane surface. 

Fig. 164 shows a micrograph at 1000 diameters of such slip 
bands in a ferrite grain in malleable cast iron. Such a deforma- 



342 



American Malleable Cast Iron 



tion, increased in magnitude, may result in the rupture of the 
grain itself at right angles to the slip bands, as shown in Fig. 165, 
or by producing such a distortion of the grains that it can no 
longer articulate with the surrounding grains closely enough to 
be held to them by the cement of amorphous iron at the bound- 
aries. 

Change of Structure When Deformed 

On the other hand examination of the originally polished 
plane surface of a specimen parallel to the direction of stress 
which had failed by primary intergranular fracture would show 




Fig. 165. Intragranular fracture of a ferrite grain in malleable 

Nitric acid etch 1000 diameters 

Note that the path of rupture has advanced about two-thirds through the 

grain at right angles to the slip bands 

no slip bands but a considerable displacement of the polished 
surfaces of the individual grains from their initial location in 
the polished plane provided the failure was due to shear at 
the grain boundaries. On the other hand, if failure was due 
to forces having a tensile component normal to the grain 
boundary, the separation of originally adjacent grains would 
be shown. 

Where the conditions have been such as to produce fairly 
great plastic deformation it may even be possible to note the 
effect of intragranular flow in the changed orientation of the 
polygons marking the individual grains. 



Plastic Deformation 



343 



In unworked ductile metal there is no preference as to the 
direction of the longer diameters of the grains in any given 
surface nor are the diameters in various directions widely 
different. After plastic deformation however the originally 
equi-axed grains may be flattened into sheets, drawn out into 
threads, etc., etc., depending upon the character of the stress 
and the direction of the stress with reference to the polished 




Fig. 166. Intergranular failure of malleable 

Nitric acid etch 400 diameters 

Note that the surfaces of the different grains no longer seem to be in the same plane 



surface under examination. Of course it is obviously necessary 
that such changes of form can be detected best in a plane 
parallel to the direction of load and are visible only as changes 
of grain size in a plane normal to the deforming stress. 

Microscopic examination of the path of rupture through a 
metal, of the deformation of grains under load or, when applied 
to surfaces prepared before the application of the stresses, of 
intragranular slip and intergranular displacements is capable of 



344 American Malleable Cast Iron 

interesting disclosures as to the mechanism of plastic deforma- 
tion or ultimate failure under various types of stress. 

Shows Two Systems of Slip Bands 

A very cursory summary of the changes in malleable is at- 
tempted in the accompanying photomicrographs. .Fig. 166 shows 
an unusual failure of intergranular type. It will be seen that 
at several points the grains have the appearance of being above 
or below the general surface. These grains have slipped not 




Fig. 167. Ferrite grains in malleable, showing slip in two planes at right 

angles 

Nitric acid etch 400 diameters 

Note the cohesion at grain boundaries even after severe plastic deformation 

on the crystal faces within the grains but at the surface of 
contact of adjacent grains. The field of view is near the com- 
pression side of a piece distorted by cross bending and it is pos- 
sible that this slip at grain boundaries produces the white so 
called compression fracture. The comparative absence of slip 
bands is interesting. 

Fig. 167 is reproduced from the tension side of the same piece 
and shows well developed bands. In some grains two sys- 
tems of bands are seen due to slip along two directions. The 
fact that the adjacent grains are not separated even under 
heavy strain shows the strength and ductility of the amor- 
phous boundary. 

Fig. 168, taken from a piece loaded in pure compression, 
shows that the structure of Fig. 166 is not always characteristic 



Plastic Deformation 



345 



of this type of loading and also shows plainly two systems of 
slip bands in practically every grain. In all of these photo- 
mi'crographs, note that the direction of slip is constant in any 
given grain, but is not usually the same in adjacent grains. The 
direction of slip has no direct relation to the direction of the 
stress but is determined by the direction of the crystallographic 
axis of the ultra microscopic crystals making up the individual 
grains. 

Figs. 169 and 170 show the distortion of grains in compres- 




Fig. 168. Slip bands due to plastic compression in malleable iron 
Nitric acid etch 500 diameters 

sion as seen on a polished section parallel to the direction of 
stress prepared after the distortion has occurred. The grains 
are much flattened as are the nodules of temper carbon. The 
grain boundaries are nearly obliterated but there is no separation 
of the adjacent grains. The effect is more strongly marked 
at the axis of the specimen than near the surface due to the 
fact that the barreling out of the specimen has permitted part 
of the reduction in height to be made by bending the outer 
fibers instead of upsetting them. The specimen from which these 
illustrations were made was compressed to a little less, than 
one-half of its original height. 

The effects of plastic deformation upon the grain structure 
can be destroyed by somewhat prolonged heat treatment below 
the critical point. By such treatment a new series of equi-axed 



346 



American Malleable Cast Iron 




Fig. 169. Plastic deformation of malleable in compression 
Nitric acid etch 100 diameters 

Field near axis of the specimen in a plane parallel to the stress. Note the flattening 
of ferrite grains, faint grain boundaries and distortion of temper carbon 

grains is formed, whose size depends upon the degree of the 
previous plastic deformation and the heat treatment adopted. 
Fig. 172 shows an axial section of a specimen similar to that shown 
in Fig. 169, after about five hours at 650 degrees Cent. While 
the ferrite becomes equi-axed and fine grained the deformation 
of the temper carbon still persists. 

Path of Rupture Shown 

Fig. 171 shows the path of rupture of malleable broken in 
cross bending. It was prepared by breaking a wedge-shaped 
piece by bending it over until fracture occurred. The fracture 
was then plated with copper, the specimen sawed in two at 
right angles to the ruptured surface and parallel to the cross 
bending stress and the exposed surface polished. 



Plastic Deformation 



347 




Fig. 170. Same specimen as shown in Fig. 169 

Nitric acid etch 100 diameters 

Field near surface of specimen in plane parallel to stress. Note the difference from 

Fig. 169 in lessened intensity of all changes 

It is particularly interesting to note how the path of rupture 
goes far out of its way to include temper carbon nodules. This 
makes many deep depressions in the broken surface and due to 
the shadows in the bottom of these depressions produces the 
characteristic black fracture of the product. It is not often 
recognized that the presence of temper carbon is not a suffi- 
cient explanation of the black fracture -for this material, rep- 
resenting about 6 per cent of an average cross section, would 
not be nearly sufficient to darken the surrounding silver white 
metal. 

It is only due to the fact that the plane of rupture takes 
in many more nodules of carbon than would be found in an 
average section and in so doing produces a ,sort of "nap" that 



348 



American Malleable Cast Iron 




o c ^, 

3 <u In 

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CJ 3 

03 r^ 

uT CTj 



8 -3 



a 3 



O v- i 
'*' 



CO U| "- M 

t fl 



be 



- 

& H 



Plastic Deformation 



349 



the fracture appears as dark as it does. A fracture running 
at random along grain boundaries would be steely and crystalline 
in character. 

The mechanical effects of plastic deformation offer a most 
interesting field of investigation. Most engineers are acquainted 
with the effects produced by cold rolling on steel and brass rods 
and sheets, and by cold drawing on copper and iron wires ; the 




Fig. 172. Malleable iron compressed about one-half. Annealed 5 hours 

at 650 degrees Cent. 



hardening is a consequence of the distortion of the metallic 
grains. 

Beilby's theory suggests that the change in properties is caused 
by formation of amorphous iron due to the partial destruction of 
the normal crystal structure when this becomes distorted. In 
this view the greater the coldwork the more nearly does the ma- 
terial as a whole assume the properties of this noncrystalline 
iron, Jeffries and Archer have dealt ably with the relation be- 
tween slip and hardness in an article appearing on page 1057 



350 American Malleable Cast Iron __ 

of the June 15, 1921 issue of Chemical and Metallurgical En- 
gineering. 

For the purpose of the present study we may dismiss from 
consideration the more abstruse theoretical considerations and 
assume it to be an experimentally determined fact that metal 
which has suffered plastic deformation has become permanently 
altered as to its physical properties. 

As a matter of fact this premise is of far reaching effect. 
Although it is becoming more and more usual to base engineer- 
ing design upon the elastic limit rather than upon ultimate 
strength, still there always remains the possibility that a struc- 
tural detail will be subjected, during manufacture or in use, to 
stresses which although insufficient to produce rupture will 
produce plastic deformation and the accompanying changes in 
physical properties. 

In utilizing a given specimen of a ductile metal we must 
consider not only the normal physical properties of that metal 
but its entire previous history with respect to applied stress 
and also its subsequent service in so far as that is predictable. 

In the case of pure iron chemical means are available for de- 
tecting the presence of plastic deformation. The products of 
the reaction between nitric acid and unstrained iron differ from 
those if the iron has suffered strain. An analysis of the reaction 
products thus will permit of conclusions as to the conditions of 
the metal. The method has not yet been applied to malleable 
owing to the disturbing effect of the residue of graphitic car- 
bon. 

We might assure ourselves of the absence of cold work by 
a heat treatment just, before use but this is impracticable. For 
the purpose of the designer and manufacturer we must assume 
that the behavior of any ductile material in service involves each 
stress applied in its previous history and not single stresses. 

It is possible that the entire problem is so complex that a 
clear understanding of the effects of sequences of stress is be- 
yond our grasp. Four cases can be distinguished: 

1. The stresses in the sequence differ neither in character, 



Plastic Deformation 351 

magnitude or sign. This may be illustrated by a load which is 
alternately applied and removed. 

2. The stresses do not differ in character or sign, but differ 
in magnitude. A load that is constantly applied but varies in 
intensity is an example. 

3. The stresses do not vary in character but vary in mag- 
nitude and algebraic sign. Such a condition could be caused by 
alternate compression and tension, crossbending in opposite direc- 
tions as in rotating beam test, torque in opposite directions etc. 

4. The stresses vary with respect to all three characteristics. 
This would be the case if torque were followed or preceded by 
tension or compression or if compression in one direction were 
followed by tension or compression at right angles thereto, etc. 

The ever increasing complexity possible will be readily ob- 
served. To this complexity must be added the fact that ac- 
cording to Nutting's conclusions the stress under plastic deforma- 
tion is a function of the time of application. 

A formal study of the entire phenomenon therefore is 
scarcely possible by any individual or laboratory; indeed the 
vast amount of work which has been done in impact and fatigue 
testing has but incompletely studied a small portion of this im- 
mense field. 

New Data Is Available 

It is therefore with humility that the author ventures to 
record certain observations, not much better than qualitative in 
character, on some of the mechanical effects of plastic deforma- 
tion of malleable. According to the Nutting formula the strain 
under plastic flow is proportional to a higher power than unity 
of the applied stress and to a fractional power of the time of 
application. 

Up to the proportional limit, the deformation is elastic and 
proportional to the stress. The exponent of the stress is unity 
and not greater than unity and the strain does not depend upon 
time. The exponent of time is zero. The course of the usual 
stress strain diagram, in tension, for malleable seems to in- 
dicate that, for rather quickly increasing stresses the plastic 
deformation of malleable is approximately proportional to the 
sixth power of the applied stress. There is a surprisingly 



352 



/Inter lean Malleable Cast Iron 



Slow Is At The Rote Of .0000157 Per Minute 
FasMsM Thetfate Of .Ob" Per Minute 




.02 .04 .06 .08 .10 .12 .14 .16 .18 .20 .22 
fc"0 .0004 .0008 .0012 0016 .0020 .0024 .0028 .0031 .0036 .0040 .0044 .0046 

Eionqotion 



Fig. 173. Stress strain diagram .of malleable iron in tension for two 

rates of loading 



short transition range between the point where the strain is 
directly proportional to the stress and the point where it begins 
to be proportional to the sixth power. 

Stress Exponent Changes 

During the transition range the exponent of stress obviously 
changes progressively from 1 to 6. To illustrate the effect of 
time on plastic deformation two stress strain diagrams are 
shown in Fig. 173. In one of these the diagram was made rapidly 
as extensometer readings could be taken while in the other each 
increment of load was maintained till no further increment of 
length was observed. In the former case the time was perhaps 
four or five minutes ; in the latter case it was 250 hours. 

It is obvious that if quickly loaded, to moderate stress, 
the metal will be stiff er than if the stress must be endured in- 
definitely. The ultimate strength and elongation are unaffected 
however. In Fig. 174 is shown the progress of deformation 



Plastic Deformation 



353 



with time at two intensities of stress, in each case the last 500 
pounds increment of load having been applied only after equili- 
brium had been attained under the previous load. In Fig. 175 
a similar graph is plotted for behavior under a quickly applied 
load well above the yield point. Below the proportional limit 
no increment of strain with time is observed stress being 
constant. 

Having thus given concrete examples of the application 
of the Nutting hypothesis to this particular metal we may turn 



8,500 Lb5. Per 5o. In. 



29,500 Lb5. Per So. 



Chances of Strain with Time 
at Small Increment of Stress 




.001 .002, .003 .004 .005 .006 .007 .008 .009 .010 .Oil 

Elongation in Inches Over 6" 



Fig. 174. Changes of strain with time at small increment of stress 



354 



American Malleable Cast Iron* 



to the effect of previous tensile stresses to the stress-strain re- 
lationships during subsequent stresses of the same character. 

It is well known that a material to which a tensile strength 
in excess of the elastic limit has been applied, thereafter has 
an elastic limit equal to the previous load. The stress-strain 
diagram under successive increasing tensile stress is shown in 
Fig. 176. It will be seen that up to the proportional limit the 
stress leaves no permanent effect. On releasing a stress which 



.036 




Curve 15 Ap 



2.016 

| 

gOK 

^.008 

.004 



10 IE 14 16 18 SO 11 4 
Time in Hours 



30 



Fig. 175. Changes of strain with time under considerable increment of 
stress (about 70 per cent of ultimate strength) 

has produced plastic deformation the material contracts elastic- 
ally, retaining a permanent set. Under a subsequent load it 
stretches elastically up to the previous maximum and then be- 
yond that deforms according to a typical plastic deformation 
curve. 

A similar cycle is repeated for each subsequent load, pro- 
vided the previous load is exceeded. If not, then the metal 
merely deforms elastically. A corollary seems to be that no 
work is absorbed by the metal except during the plastic defor- 
mation, hence it is difficult to see how the material could fail 



Plastic Deformation 



355 



in fatigue by repetitions of any tensile stress which is of suf- 
ficient intensity to cause rupture on its first application. Dalby 
finds that although the speciman appears perfectly elastic on 
successive loadings actually no part of the curve on unloading 
or reloading is a straight line but the two form a series of 
loops one for each repetition which of course amount to an ab- 



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ClongoTion In fight Inches 



Fig. 176. Stress strain diagram of malleable iron in repeated tension 
under increasing loads 



sorption of energy. Similar loops can be observed in malleable 
if the magnification be sufficient. They are barely visible in 
the diagram. 

The simplest case of stress reversing in algebraic sign is that 
alternating between tension and compression of equal intensity 
although alternate torsional shear is also of considerable im- 
portance. We have seen in the earlier chapters of this series 
that the behavior, at least within the elastic limit, of malleable 



356 American Malleable Cast Iron 

in tension and compression, is similar; the proportional limit, 
being about 15,000 pounds per square inch and the modulus 
of elasticity about 25 x 10 6 pounds per square inch. Thus there 
is an elastic range of about 30,000 pounds per square inch, 
one half on each side of the neutral or unloaded condition 
through which the intensity of stress can be varied without 
plastic deformation. 

Applying Alternate Tension and Compression 
One of the simplest experimental methods of applying 
alternate tension and compression to a specimen is that of 
bending a beam to and fro in opposite directions. The be- 
havior of malleable under cross bending stresses has already 
been fully considered, notably the fact that ultimate strength 
and elastic limit determined in this manner bear no direct re- 
lation to these constants as determined in pure tension and com- 
pression. The explanation of this observation has also been 
detailed. 

The graph in Fig. 176 indicates the response of a malleable 
beam nominally J/ -inch' wide and 1-inch deep on supports 10- 
inches apart to alternations of stress. The deflections are plot- 
ted against apparent maximum fibre stress, as calculated from 
the known dimensions of the specimen and the applied load. 
When as the apparent proportional limit is not exceeded, the 
stress-strain diagram under this cyclic cross bending is merely 
a straight line through the origin at an angle depending upon 
the modulus of elasticity o the metal. However,, when the 
load in either direction exceeds the proportional limit the stress 
strain diagram becomes a curve, plastic deformation taking 
iplace. As the specimen is unloaded the elastic deformation 
alone is removed and at zero a certain permanent set equal 
to the plastic deformation remains. 

Elastic Limit Increases 

The effect of this plastic deformation is represented not 
only by the measurable permanent set but also by the increased 
elastic limit in the direction of the previously applied load. 
On reversing the direction of stress the elastic limit is en- 
countered sooner than it should be and the plastic deformation 



Plastic Deformation 



357 



begins at a lower stress than was the case in the unstrained 
metal. 

When an intensity of stress equal. to the previous maximum 
but of opposite sign is attained in a perfectly homogeneous 
specimen, an equal and opposite strain would ensue although 
in the present case the negative deflections all seem somewhat 



?25 50 37.5 W l5 12.5 5 57.9 50 62.5" 
6tre55ln Thousand Pounds Per SOuare Inch 




Fig. 177. Behavior of malleable under cyclic bending under increas- 
ing loads 

less than the corresponding positive ones. 

Action of Specimen 

On unloading the specimen it straightens out first elas- 
tically, retaining a negative set at zero load. Under reversed 
loads it finally .deforms plastically until at the stress corres- 
ponding to the first (positive maximum) it has the original 
deflection. 



358 



American Malleable Cast Iron 



Thus the cyclic cross bending stress-strain diagram is a 
spindle shaped loop whose area represent? the work done 1 in 
plastic deformation. Plastic deformation in a given direction 
raises the elastic limit in that direction and decreases the abso- 
lute value of this constant in the opposite direction, the elastic 
range remaining approximately constant. With successively 
increasing intensities of stress the area of this mechanical 
hystersis loop grows larger and larger as shown in Fig. 177. 

If instead of applying cyclic cross bending in a manner so 
that each cycle oscillates through a wider range of stress than 
the preceding one we merely repeat a given cycle indefinitely, 
it is found that the hysteresis loop decreases in area with suc- 
cessive cycles. Fig. 178 shows the first and tenth loops of such 



c.03 



bl.5 50 37.5 25 125 12-5 5 315 50 625 

Stress In Thousand Pounds Per Square IncH 



Fig. 178. Behavior of malleable under cyclic cross bending at constant 

maximum stress 



Plastic Deformation 



359 



,160 



Maximum Deflection 




2,345 6 789 
No. of Applications 



Fig. 179. Maximum deflection and permanent set under cyclic cross bend- 
ing at constant maximum stress 

a series. The decrease in work per cycle is due to the smaller 
plastic deformation in each successive cycle due to the hardening 
of the metal from the cumulative effect of all the slip produced. 
The decrease in deflection and permanent set is not at constant 
rate but decreases with each successive loading as shown in Fig. 
179 and approaches a fixed minimum of finite size. The deflections 
and sets are shown to be different according to which half the 
specimen is in tension. This is presumably due to lack of com- 
plete symmetry about the neutral axis. The work done by a 
great number of such alternations will finally rupture the speci- 
men. This constitutes the phenomenon of fatigue. The phe- 
nomenon of fatigue of metals so far as it is known has been 
discussed in another chapter. The experiments just re- 
corded having shown the approximate extent to which tensile 
or compressive loads strengthen the material for subsequent loads 



360 American Malleable Cast Iron 

in the same direction and weaken it for loads of opposite sign. 
From these experiments we can gain at least a qualitative insight 
upon the effect of a previous cross bending upon subsequent 
tension or compression in a direction parallel to the length of 
the specimen and vice, versa. The quantitative interpretation is 
impractical perhaps impossible owing to the difficulty of ac- 
counting for the distribution of stress in a plastically strained 
material. 

Behavior of Specimen 

Consequently under the subsequently applied longitudinal 
stress the elastic limit will be first exceeded on that edge of the 
specimen which is experiencing a reversal of stress. As the 
applied longitudinal load is increased a greater and greater por- 
tion of the area experiences plastic deformation until finally the 
elastic limit also is reached at the opposite edge. 

At intermediate intensities of stress in a portion of the spe- 
cimen elastic strain exists, in another portion plastic strain. From 
the nature of the case the ratio of strain to stress is greater for 
plastic than elastic deformation. The side experiencing a re- 
versal of stress will stretch or compress more rapidly and an 
eccentricity of loading will result from the unequal strain dis- 
tribution. Such an eccentricity in the case of compression will 
result in the superposition of a bending moment on the longi- 
tudinal stress, as in the case of columns which are eccentrically 
loaded and a given load will produce far greater unit stresses 
than might be expected. 

In the case of tension the eccentricity of loading will re- 
sult in the transfer of a disproportionate amount of load to a few 
of the stiffer fibers with an accompanying high unit stress. 

Conversely the effect of a previous longitudinal stress upon 
subsequent cross bending loads is to shift the neutral axis to- 
ward that surface of the specimen which is being stressed in the 
same sense as the first load. This shift goes on until the 
moment of resistance of the portion of the specimens in opposite 
sides of the axis about the axis are equal. 

The sum of the two moments, constituting the moment of 
resistance is thereby decreased. In either event, although we 
may not be able to solve numerically the complex mechanics we 



Plastic Deformation 361 



may draw the conclusion that cross bending weakens the ma- 
terial for subsequent tension or compression and vice versa. 

The practical application of this conclusion is that a detail 
which in fabrication has been subjected to severe cold work 
cannot be expected to be as strong under loadings involving a 
reversal of the stress previously encountered as unworked metal 
would be. This conclusion applies equally to all ductile materials 
and should serve as a warning against needlessly energetic 
straightening or beading operations. Many malleable castings 
are cast to a simpler form than intended and then bent to the 
more complex shapes demanded. Air brake hose clamps are 
examples of this practice. Such parts will never develop the 
full strength of the original metal. 

In all the preceding cases the loadings have been such as 
to set up strains parallel to the subsequent stresses. A variety 
of circumstances are possible in which the final load has no 
component parallel to that producing the plastic deformation. 

Two typical cases are torsional shear followed by tension 
and compression followed by tension or compression in a di- 
rection normal to the first compression. Compression followed 
by a cross bending load parallel to the direction of compression 
is, of course, a special case of the preceding involving both 
tension and compression. 

The combination of compression followed by tension, com- 
pression, or both, normal to the original strain is the condition 
which may arise where a piece is reduced to the desired dimen- 
sions by compression in a press rather than by machining. In 
Fig. 180 are shown two stress-strain diagrams on specimens 
nominally ^>-inch square subjected to cross bending load on 
supports 10 inches apart. One specimen, A, is of normal metal 
in its original condition, while the other, C, was produced from 
a thicker bar by compressing it to a final depth of J/ inch. 
The compressed dimension is vertical, that is, parallel to the 
direction of the load in the final test. The effect of relatively 
heavy compression under these circumstances can be learned by 
a comparison of the two graphs. 

A few scattering tests of the effect of shear upon subse- 
quent tensile stress have been made. 



362 



American Malleable Cast Iron 



In Fig. 180 certain tests of this character are tabulated. 
Standard A. S. T. M. tension specimens were twisted through 
various angles and then broken in tension. In the illustration the 
angle of twist under load is plotted against the tensile properties 
of the resulting metal. 

It will be noted that a rapid and continuous decrease in 
elongation is encountered with increasing torsional deformation. 
The tensile strength first rises rapidly to a maximum and then 
decreases still more rapidly. The location* of the maximum 



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Fig. 180. Stress deflection diagram of malleable in cross bending with 
and without previous cold work 

tensile strength corresponds approximately to the torsional yield 
point, as may be seen from the torsional stress strain diagram. 
The curve suggests a hardening of the metal due to the forma- 
tion of amorphous metal followed at higher strains by disrup- 
tion at the grain boundaries. 

Failure in tension after great torsional strain did not result 
approximately normal to the axis but in a spiral surface ap- 
proximately normal to the helix angle into which the originally 
straight elements of the specimen have been strained. There is 
a suggestion here that distortion is not due to pure shear. 

We have considered the effect of a series of stresses of 
known intensity and direction upon a ductile material. Another 



Plastic Deformation 



363 



important condition is that in which, instead of a series of 
known stresses the specimen is required to undergo a series of 
known increments of energy. 

Impact testing by a series of equal or increasing blows, 
is the principal application of this type of plastic deformation. 




90 180 70 360 450 540 680 7EO 6)0 900 990 1080 
Angle Of Torsion (Degrees) In 4' Goqe Length 



Fig. 181. Effect of torsional deformation upon subsequent tensile strength 

of malleable 



In this case the intensity of maximum stress is a function both 
of the energy input of the blow and the elastic and plastic de- 
formation of the specimen. The latter factor depends upon the 
previous plastic deformation of the specimen and hence is a 
function of the magnitude and number of the preceding series 
of inputs of energy. 



364 



American Malleable Cast Iron 



Since malleable is often subjected to repeated impact in serv- 
ice and occasionally in testing, this condition is of special im- 
portance in connection with a study of that metal. 

If the load deformation curve of a given specimen under 
plastice deformation were capable of mathematical definition in 
terms of its dimensions and properties and the rate of applica- 
tion of the load, a mathematical study of this problem would 
be feasible although probably quite complex. 

However, the problem may be simplified by assuming that 




Pef/ecfrtn 



Fig. 182. Absorption of energy from successive impacts 

we have experimentally determined the load-deformation dia- 
gram of a given specimen under given conditions. The load- 
deformation diagram in every respect is similar to a stress- 
strain diagram except that the co-ordinates are actual load 
and actual deflection instead of unit stress and unit strain. We 
can conceive that for a given specimen such a graph might be 
autographically produced under rates of application of load 
as rapid as are encountered in impact testing. 

Referring to Fig. 182 let OLU represent the load-deforma- 
tion curve described above, L being the elastic limit and U , the 
ultimate strength and tan the modulus of elasticity. Then the 
energy imparted to the specimen at any given load and deforma- 
tion for instance is the area below the curve beginning at O 



Plastic Deformation 365 



and ending at a n . For example, OLa a 2 etc., a n b n . If this energy 
input be large enough the point a n will then reach U, the energy 
being the represented by OLa^a 2 etc., UV and this energy will 
produce rupture under impact. 

Therefore, if impact is produced by a single blow, the en- 
ergy of rupture is measured by the entire area below the curve 
as shown above. A blow having an energy of impact of OLM 
or less will not produce a plastic deformation, the specimen will 
return to its original form after the load is removed and will 
have absorbed no energy. If the energy of impact be equal to 
OLaJ)i for example, when the load is removed the deformation 
will decrease along a^ (parallel to OL) and a permanent set 
Oci will remain. The energy OLa^c^ will have been used up 
in plastic deformation and the elastic limit will be raised to a 1 
and the deflection at the elastic limit to c-J)^. The new load de- 
flection curve becomes caa etc., UV. Thereafter any impact of 
energy not greater than c^ajb^ will produce elastic deformation 
only. Suppose the second impact is equal to C 1 a 1 a 2 6 2 then by 
similar measuring the new load deflection curve becomes C 2 a 2 a 3 a n 
etc., UV the third impact moves it to c 3 a 4 a n etc., UV and so on, 
and after n blows it becomes c n a n UV and finally perhaps WUV 
in which case a blow equal to or greater than WUV will break 
the specimen. 

Suppose now that we assume an equal energy input with 
each blow. Then OLaJb^ C 1 a 1 a 2 & 2 = C 2 a 2 a 3 b 3 etc., 
cn- 1 an- 1 an bn. It is obvious by inspection that up to the point 
of maximum load G each succeeding one of the similar tri- 
angles caji, C 2 a 2 b 2 etc., is of larger area than its predecessor. 
These triangles represent the portion of the energy of impact 
expended on elastic deformation. Consequently a smaller per- 
centage of the constant increment of energy is available for 
plastic deformation with each succeeding blow up to that pro- 
ducing maximum deflection. Beyond this point an inqreasing- 
ly larger amount of each energy increment is available for plastic 
deformation. 

Finally if ^c^a 2 c 2 + C 2 a 2 a 3 c 3 c n .^an ^a n c n etc., is com- 
mensurate with OLGUW the specimen absorbs on the last blow 
energy equivalent to UVW '. 



366 American Malleable Cast Iron 

The specimen has then absorbed plastically the energy 
OLGUV which it would have absorbed if broken by a single 
impact. Since, however, the area Cn-^n^an c n is always less 
than the area c,,.^,.^^ b the energy absorbed by the metal 
at each blow is measurably less than the total energy of im- 
pact, a large part of the energy of impact being returned by the 
specimen during its elastic recovery. 

Obviously since there is a definite amount of energy not ab- 
sorbed by the specimen at each blow a smaller percentage of the 
energy of impact is absorbed the lighter the blow. If the energy 
of rupture be measured by the aggregate of the energy of the 
entire number of blows to produce rupture this sum will be 
higher the smaller the individual blows. Consequently testing 
a metal by successive impacts can yield quantitatively compar- 
able results when all the specimens are identical in form and 
quality in addition to the constancy of the hammer blow. Of 
course this condition is impracticable of attainment, the quality 
being unknown before the test. 

In practice this means that only carefully prepared speci- 
mens of similar material are capable of fairly accurate com- 
parison by repeated impact test. 

One or two further conclusions may be gained from the 
study of the diagram. Energy equivalent to the area OLM 
is absorbed by the specimen elastically. The material will with- 
stand an indefinite number of impacts of this magnitude with- 
out permanent deformation. 

Were a similar triangle FGH drawn with its apex at G , 
this area will represent the maximum elastic absorption of 
energy the specimen can sustain when by repeated impact the 
elastic limit has been raised to the ultimate strength. Any 
increment of energy less than this will never fracture the 
piece but will produce a maximum deflection after a given 
number of blows which will not be further increased by further 
repetitions of the impact. 

The area OLM LM. LM tan 0=modulus of elasticity X 
square of elastic limit. 

The area FGH = GH. CH tan 0=modulus of elasticity 



Plastic Deformation 



367 



X square of ultimate strength. 

From the above we may calculate the blows required to 
make an impact test workable on a given specimen. 

The deflection at each successive blow can be determined 
graphically under given conditions from the diagram. An 
impact test in which the energy increment increases with each 
blow can be studied in a similar manner. In that case there is 
no possibility of coming to a maximum deflection without frac- 




Fig. 183. Load deformation diagram of. specimen subjected to alternate 

impact 

ture for the increased energy of the succeeding blow would 
carry the deformation beyond G. In such a test there is great 
danger that the last blow will be equivalent to far more than the 
energy WUV and the unabsorbed energy of the blow will be 
credited also to the specimen. 

We may generalize to the effect that no method of repeated 
impact can correctly measure the energy of rupture of a duc- 
tile metal. In a similar manner we may study graphically the 



368 American Malleable Cast Iron 

effect of alternate impact in opposite directions, although we 
may be confronted with the difficulty of securing the necessary 
load deformation curves. In Fig. 183 U^L^OLU is the original 
curve for the specimen. An increment of energy Oa^b^ de- 
forms it to a and raises the elastic limit to that point. The 
load-deformation diagram then becomes a- l O- l L L JJ' 1 ^ and an in- 
crement of energy in the opposite direction to the first O l L 1 1 a 2 b. 2 
produces a load of a 2 b 2 and a deformation O^b^ The new 
elastic limit becomes a 2 and the new diagram a 2 O 2 U 2 . 

The next increment of energy is diagramed as O 2 a 3 B 3 and 
so on. It will be seen that each impact in one direction appar- 
ently decreases both the ultimate load and elongation in the op- 
posite direction an expression of the weakening caused by a 
negative plastic deformation. 

In the absence of stress strain diagrams under dynamic 
loads we may turn as the best available substitute to the vari- 
ous stress strain diagrams given throughout these chapters and 
from them and the dknensions of the specimens estimate the 
probable load deformation curves to be used. 

It is obvious that those materials in which the elastic limit 
is quite high accompanied by a high elongation are these which 
will well resist repeated impact. The high elastic limit will dissi- 
pate a large amount of energy in elastic deformation at each 
blow while the high elongation provides a large amount of re- 
serve energy for plastic deformation before rupture takes place. 

The Young's modulus of all ferrous materials is practically 
the same, hence the deformation at the elastic limit is in direct 
proportion to the elastic limit. In steel high elastic ratio is ob- 
tained only at the expense of elongation and vice versa. The 
various graphs for malleable, indicating a constant and high 
elastic ratio and an elongation increasing with strength account 
for its excellent behavior under repeated impact even when of 
sufficient magnitude to produce plastic flow. 

In this connection, incidentally the yield point of metal 
is the governing factor in ferrous materials for the small reduc- 
tion in the area representing energy clue to the curvature of 
the stress-strain diagram between the proportional limit and 
yie!cl point is negligible. 



Plastic Deformation 369 



Plastic deformation has been discussed mainly because of 
its great importance in the utilization of malleable. No one 
realizes more than the author the unsatisfactory state of 
knowledge and the lack of precise numerical data. If this 
chapter has enabled the reader to form even a qualitative image 
of the resistance of the metal above the elastic limit that is all 
that can be expected. An infinite amount of further study will 
be required before concrete mathematical analyses will be 
possible. 



XIX 

THERMAL AND ELECTRICAL PROPERTIES 

WHILE it is true that materials of construction in gen- 
eral are used to resist mechanical stress, yet there are 
service conditions when other properties, such as ther- 
mal, chemical or electrical, for instance, are of greater conse- 
quence. 

The most important condition of this kind arises in the 
use of malleable as a material for field frames of electrical 
apparatus, where the magnetic characteristics of the metal 
are much more important than the mechanical strength. It 
is a well known fact that if a coil o wire is wound around 
a piece of iron and a current is passed through the coil, the 
iron becomes magnetic. This property of iron, which it shares 
in a very limited degree with a few other metals, is of im- 
portance in electrical machinery. If the power to become 
magnetic is the quality desired, evidently the metal which forms 
the strongest magnet with the same coil and current is the 
most valuable. Therefore it is desirable to determine the de- 
gree to which a given material possesses this valuable property. 
Avoiding a discussion of the electrical principles and of the 
mathematical reasoning involved in the study of magnetism, it 
is sufficient to say that the intensity of magnetization, repre- 
sented by the symbol H f and expressed in gausses (lines per 
square centimeter) can be calculated from the dimensions of a 
magnetizing coil and measurement of the current. When an 
iron core is inserted in the coil it will be found that the inten- 
sity of magnetic field is much greater than the calculated value 
H. This higher value, known as magnetic induction, is sym- 
bolized as B and is measured in the same units as H. The 
ratio of B to H, that is, the number of times stronger the 
magnet is with the iron core than without any core, using the 
coil only, is called the permeability of the material and is the 
variable represented by the Greek letter /*. 

It is further found that the value of /* depends not only 



372' American Malleable Cast Iron 

upon the material 'being used but also on the value of H at 
which the experiment is made. In general, the permeability 
of a material first increases as H increases, soon reaches a 
maximum and then falls off, first rapidly and then more and 
more slowly. 

The value of /* for an indefinitely strong field is prob- 
ably 1 for all materials. Owing to experimental difficulties 
determinations close to the zero value of B are not very 
reliable. The behavior of a magnetic material is usually repre- 
sented by a so-called magnetization or "B-H" curve in which 
the value of H, the strength of the magnetic field, is plotted 
horizontally and the magnetic induction in the iron, B,, which 
is equal to v-H, is plotted vertically. The fact that /* is vari- 
able, depending on B and hence on H, gives this curve a gen- 
eral form which rises from the origin (H = 0, B =0) first 
ait a rapidly increasing rate as H increases and then more 
slowly until it becomes horizontal when H is infinite. As a 
matter of fact the curve becomes nearly horizontal fairly 
soon, and /the "knee" in the curve, somewhat resembling the 
yield point in a tensile stress strain diagram, represents practi- 
cally the maximum flux density which can be attained in a 
given metal. This value varies widely in different metals and 
is quite definite in each metal having almost the significance of 
a physical constant. This characteristic for malleable iron is 
shown in curve A, Fig. 184. The specimen was in the form of a 
closed ring about 6 inches in diameter and having a rectangular 
section 0.33-inch thick radially and 0.9-inch wide. The per- 

B 

meability, A* = 
H 

for various values of //based on the data for the ring described 
above, is shown in curve B. The values of /* as related to B 
are plotted in curve C. 

When a material has been magnetized and the magnetic 
field H is then reduced, the magnetic induction B in the 
iron decreases but not at the same rate as it increased with 
increasing values of H. When H is reduced to there usually 
remains a considerable magnetic induction and it is only 



Thermal and Electrical Properties 



373 



after H has reached a definite value in the opposite direction 
to that first developed that B falls to 0. 

This lag of induction behind magnetizing force is due to 
hysteresis. The value of B when H is reduced from a high 



500 



10000 



CO 5000 




500 



10 20 3 40 

H in C.G. 5. Units 



Fig. 184. Magnetization and permeability curves of malleable cast iron 

value to is called residual magnetism, and the negative value 
of H required to bring B to is called the coercive force. 
It is quite possible to plot a curve, similar to a B-H curve 
beginning with a fairly high value of H, lowering H gradually 
to 0, then increasing it in the opposite direction until a nega- 
tive value is reached equal in magnitude to the original posi- 
tive value, then back through to the starting point. Such a 



374 American Malleable Cast Iron 

curve forms a closed loop of distinctive form called a 'hysteresis 
loop. The area of this loop represents energy consumed in 
magnetizing and demagnetizing the specimen. Materials strong- 
ly retaining their magnetism, and therefore suitable for per- 
manent magnets have a larger hysteresis loop due to great 
residual magnetism and coercive force. Material for electro- 
magnets, especially where frequent changes in magnitude or 
sign are required in field strength have the opposite characteris- 
tics. 

This energy is dissipated as heat, either in raising the tem- 
perature of the iron or radiated to the surroundings. The 
loss is of industrial importance for service involving reversals 
of magnetism in that it involves a waste of energy and may re- 
sult in inadmissably high temperatures being reached in the 
magnetic circuit, possibly sufficient to destroy the insulation on 
the coils. The energy is lost once for each cycle of magnetiza- 
tion so that for alternating currents the loss depends on the 
frequency. 

It can be shown mathematically that the energy dissipated 
per cycle of magnetization per cubic centimeter of metal is 
the area of the hysteresis loop divided by 4 71 ", regard being had 
of course to the scale to which B and // are plotted. This 
value is necessarily dependent on the magnetic induction ob- 
tained. In Fig. 185 a condition is plotted in which saturation 
has practically been attained, hence calculations based on 
this graph would give the energy dissipated by a complete 
cycle. The area actually corresponds to a value of 11,388 
ergs per cubic centimeter of metal. Cyclic magnetization of 
malleable to an inductance of 13,200 centimeter-gram-second 
units by the usual 60-cycle alternating current would raise the 
temperature of the iron a little over 2 degrees Fahr. per minure, 
assuming no radiation of heat. 

Steinmetz has determined empirically that the work done 
in a cycle of magnetization on any given material is approxi- 
mately proportional to the highest magnetic induction, B reached 
(in the cycle raised to a power between 1.66 and 1.70. This 
formula serves to derive the work done on the same material 
by cycles ending at different inductions. Therefore, the u v- 



Thermal and Electrical Properties 



. 375 



/ Current in Ampere^ 
n* Number of Turn;, 




12000 



20 - 20 

Intensity of Magnetization, H 



40 



Fig. 185. Magnetic properties of malleable cast iron 

teresis loss on any given material, is a constant times J5 1 - 68 
when B is the maximum induction reached in the cycle. This 
constant varies with different materials and is designated by 
the Greek letter ^. Calculation from the preceding data gives 
a value of 0.00136 for Steinmetz's constant. 

This very low value is logically due to the fact that the 



376 American Malleable Cast Iron 

bulk of a malleable casting is a fairly pure ferrite contaminated 
mainly by silicon whose presence is an advantage and also to 
the fact that the anneal involves a heat treatment consistent 
with the very softest condition of ferrite possible. So far, the 
writer knows of no case where the electrical resistance of mal- 
leable is of commercial importance. It has been roughly deter- 
mined to be 0.000044 ohm per centimeter cube. More recent 
and accurate data indicate the specific resistance to be 0.0000295 
ohms per centimeter cube. A part of this descrepancy no doubt 
is due to the heterogenous character of the material. The 
newer value however is much more reliable. Presumably the 
resistance decreases with the carbon content. 

The change in resistance with temperature is shown in 
Fig. 186, the resistance at room temperature being taken as 
unity. 

Where metal parts are exposed to weather or to the action 
of water or steam, circumstances arise in which the resistance 
of the material to rusting is of prime importance. This is 
particularly true under circumstances which preclude the use of 
paint, galvanizing and similar means for protecting the metal. 

This opens up the moot subject of corrosion of iron and 
the relative merits of accelerated tests in dilute acid as com- 
pared with service tests. All commercial iron alloys, except 
a few high-silicon metals, dissolve in acids more or less rapidly. 
While not at the same rate for all forms of iron and steel 
the deterioration is rapid enough to preclude the use of ordinary 
ferrous materials for corrosion resisting services. 

A great many acid corrosion tests have been conducted on 
malleable but the results are hardly applicable to the present 
discussion. It is generally admitted that since corrosion is an 
electrolytic phenomenon, the more nearly homogeneous a metal 
is the better it will resist corrosive action either of the elements 
or of acids, salt water, etc. 

Manganese sometimes is alleged to be an offender in start- 
ing corrosion. The surface of a malleable casting is always 
nearly carbon free; it contains rather small amounts of man- 
ganese, less than any material except wrought and ingot iron. 
Silicon is supposed to dissolve in ferrite, when present in mod- 



Thermal and Electrical Properties 



377 



erate amount. It would appear therefore that malleable should 
resist rusting moderately well. This general conclusion is 
borne out by the fact that malleable has been used for many 
years in the manufacture of pipe fittings, radiator nipples, etc., 
and complaints that the material has failed by rusting are very 
rare. 



Resistance at Temperature tr Resistance at Room Temp. 

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100 200 300 400 500 600 TOO 
Degrees Cent. 



Fig. 186. Variation of electrical resistance of malleable cast iron with 

temperature 

There is also of record the case of a malleable iron harness 
part which was found in excavating for a foundation. The 
circumstances were such as to make it certain that the article 
had been in the soil over 40 years, yet it had suffered buft little 
injury to the surface. The only service test with which the 
writer is familiar was conducted to determine the relative life of 
malleable and steel railway tie plates. Plates of both ma- 
terials were laid in the same track at the same time. When 



378 American Malleable Cast Iron 

the steel plates had completely rusted away the malleable plates 
were still practically in their original condition. It seems rather 
doubt full whether in the present state of our knowledge any 
quantitative method exists of measuring resistance to corrosion 
other than a direct comparison under the conditions expected 
in practice. 

In a great many cases mechanism is required to function 
under temperature conditions either abnormally high or ab- 
normally low. The principles to which malleable owes its 
properties indicate obviously that malleable cannot be ex- 
posed to temperatures above Ac^ even momentarily, without 
being permanently destroyed. 

The question of its use at high temperature cannot be 
dismissed merely with the statement that it should never be 
exposed, even momentarily to temperatures higher than say 
1300 degrees Fahr. lest by chance Ac be overstepped and a 
permanent change be produced in the metal. There are many 
cases where castings are to be used at temperatures considerably 
below the danger point and the designer -must guide himself 
by the effect of temperature on the properties of the material. 
Even so simple a property as the dimensions of a casting are 
affected by variations of temperature. Experiments by the 
author have shown that if L be the length of a malleable cast- 
ing at degrees Cent, when the casting is raised to a tem- 
perature of t degrees Cent, its length L t will be given by the 
equation 

L t = L (1-KOQ0006 H- -0000000125 t 2 ) 

Translating into terms of Fahrenheit temperature the re- 
vised formula becomes 

L t =L 32 [1+. 0000033 (/ 32)+. 00000000385 (t 32 ) 2 ] 

These figures are somewhat cumbersome. For engineering 
purposes it may be more convenient to take the expansion at 
various 'Fahrenheit temperatures in per cent of the length at 
75 degrees Fahr. from the graph, Fig. 187. It is to be noted 
that the change in size of large castings where raised to mod- 
erately high temperatures is quite significant. Thus a cast- 
ing 3 feet long when raised to 600 degrees Fahr. expands 
over 0.1 inch which may be very important where clearances 



Thermal and Electrical Properties 



379 



are to be allowed. 

The author is not aware of any actual or experimental 
determinations of the specific heat of malleable cast iron. Since 
the material is a mechanical mixture of graphitic carbon and 
nearly pure iron we may use provisionally data calculated from 
the known constants of the two elements. 

The conductivity of a metal for heat represented by the 



0.30 

0.60 


& 

i 

|0.40 
a. 

K 
UJ 

s 

* Jj 

0.20 


C 






DC 
m 



ir 


I 

tted Curve Plate the V 
the Equation if=L ( 
where L - Length a 
Lf - 
pansion Measured '/ 
Percentage of Leng 


ilue 0. 
l+0.< 

to*c 
tc 

nS'Re 
that 7 


000006 
700006 

corded 
'5'F 


t + O.OOL 

t+o.oa 


\ 

1000012 
OOOOOli 


st* 

>5r 2 ; 




/ 


( 


/ 


^ 








/ 


/ 




















/ 


/ 




















[/ 


V 


















2 


/ 


















^i 


/ 


X 
















^o* 


' 


X 




















) 200 400 600 800 1000 1200 
Temperature, dcg Fanr 



Fig. 187. Expansion of malleable cast iron 

symbol k is defined as "the quantity of heat, in small calories 
transmitted through a plate 1 centimeter thick per square centi- 
meter of surface when the difference in temperature between 
the faces is 1 degree Cent. 

The heat transmitted through a plate of metal varies di- 
rectly as its area and as the difference in temperature between 
the faces and inversely as the thickness. 

The value of k varies slightly with the temperature, de- 



380 



American Malleable Cast Iron 



creasing for iron and increasing for carbon as the temperature 
rises. At room temperature (17 or 18 degrees Cent.) the values 
for k for iron and graphite are .161 and .037, respectively. 
(Smithsonian Physical Tables, 1921.) 

At that temperature malleable cast iron of 2 per cent to 



.006 



005 



X 



or 



05 



0' 



Fig. 188. Heat transfer from machined malleable to still water for various 
temperature differences 

total carbon should have a value of k between .1578 and .1585, 
depending on how readily heat can be transmitted from car- 
bon to iron and vice versa. 

On the same authority for the interval between 100 and 
720 degrees Cent, the value of k becomes .202 for iron, .306 
for graphite, and between .198 and .204 for malleable iron. 

The values are higher than certain approximate experimental 
values determined in the author's laboratory. Malleable heated 
above A, will have its thermal conductivity permanently de- 



Thermal and Electrical Properties 381 

creased since this constant decreases with the combined car- 
bon content. 

The specific heat of a substance is the quantity of heat in 
small calories to raise the temperature of one gram 1 degree 
Cent. 

Iron at 37 degrees Cent, has a specific heat of .1092 (loc. 
cit.) and graphite at 11 degrees Cent, a specific heat of .160. 
As a mechanical mixture of 98 per cent iron and 2 per cent 
graphite and neglecting corrections for a change of specific heat 
with temperature, the specific heat of malleable at room tem- 
perature should be .1102. The value probably is quite accurate, 
since cast iron of about 3%. per cent Cent, has a specific 
heat of .1189, The specific heat rises with the temperature. 

In view of the approximate character of these deductions 
and of their intended application a detailed study of the rela- 
tion between temperature, thermal conductivity and specific heat 
seems "unwarranted. 

All ferrous metals grow softer and weaker at elevated 
temperatures. Accordingly it becomes important to know the 
quantitative effect of temperature upon strength in order that 
where very high temperatures are unavoidable, due allowance 
may be made in design for the changed physical properties at 
the higher tempera Lures. 

Since the tensile properties can be more definitely measure.'l 
than any other, studies on the effect of temperature on strength 
have usually been made on tensile specimens. The author has 
conducted experiments of this character by breaking very care- 
fully made specimens at temperatures from 80 to 1450 de- 
grees Fahr. 

The data up to 1200 degrees Fahr. the highest commer- 
cially safe temperature to provide against the possibility of 
heating up to a temperature which will permanently affect 
the product are shown in Fig. 189. It will be seen that malle- 
able cast iron has tensile properties equal to those it possesses 
at room temperature at all temperatures from 100 to 800 
degrees Fahr. Above 900 degrees the strength decreases rapid- 
ly and at 1200 degrees the maximum allowable temperature, the 



382 



American Malleable Cast Iron 



metal is onfy one-fifth as strong as at room temperatures. Pre- 
sumably very 'similar relationships will be observed under other 
loads, compression cross bending, etc. 

Temperature affects the magnetic properties of iron. For 
large values of H, B decreases as the temperature increases; 
the reverse is true for very small values of H. The effect 
of the temperatures is not strongly marked at room tempera- 




-100 200 400 600 800 1000 1200 

Temperature j deg. Fahr 



Fig. 189. Effect of temperature upon tensile properties of malleable 

tures but increases rapidly as' the temperature goes beyond 1200 
degrees Fahr. Presumably the behavior of malleable is in ac- 
cord with these principles. Actual measurements are lacking. 
The specific heat of malleable, that is the number of heat 
units required to raise a given weight of that material 1 de- 
gree in temperature as compared with the heat units to raise an 
equal weight of water 1 degree varies from 0.11 at 75 degrees 
to 0.165 at 800 degrees Fahr. The intervening curve is near- 
ly straight, being but slightly concave upward. The values are 
calculated from the specific heats of iron and carbon. Malle- 
able, being a mechanical mixture of these two elements, can 
have this constant calculated in that way. 

As the name implies, the thermal conductivity of a metal 



Thermal and Electrical Properties 



383 



is the rate at which it will conduct heat. The constant is de- 
fined in terms of the quantity of heat conducted per unit of 
time through a cross section of unit area of a slab of unit 
thickness whose opposite sides differ by unity in temperature. 
The quantity of heat conducted varies directly as the area of 
the conductor and as the temperature difference between its 
ends and inversely as its length. However the thermal conduc- 



SJ& 



% 



J36 



4 



./<?> 



-^La6<?r<?/&s-\ 

Ht 



Fig. 190. Thermal conductivity of malleable cast iron 

tivity is not constant but varies with the temperature. 

It will be seen that the flow of heat obeys the same law 
as the flow of electric current ; indeed in a given metal the ratio 
of thermal to electrical conductivity is nearly constant at all 
temperatures. 

The determination of thermal conductivity is not alto- 
gether easy especially at high temperatures and consequently 
data on this constant are somewhat infrequent and not con- 
cordant. 

The British Aeronautical Research committee gives data 
on an annealed gray iron (1.84 per cent silicon) containing very 
little combined carbon but much free carbon as determined in 
the National physical laboratory. The committee determined 



384 American Malleable Cast Iron 

the conductivity between 40 degrees Cent, and various tempera- 
tures up to 700 degrees Cent. The data, translated into mean 
temperatures, have been plotted in Fig. 190. The conductivity 
of pure iron is shown for comparison. 

Both on account of the lower carbon content and the geo- 
metric form of the free carbon, malleable should have a higher 
conductivity than a cast iron specimen, but a lower than pure 
iron. 

The black dots in Fig. 190 give a number of observations 
by Dr. Gorton in the author's laboratory, by Wilkes' method. 
The data, while made as carefully as possible, have not always 
appeared above criticism. From the mean value of Gorton's 
data the conductivity can be taken as near .135 at 100 degrees 
-Cent. The conductivities at other temperatures have been cal- 
culated from the known thermal coefficients of electrical re- 
sistance and plotted as a line which follows very well the gen- 
eral direction of our observations. From these facts we are 
led to believe that our data may be concordant enough to have 
some utility. 

The density of malleable cast iron is occasionally of im- 
portance in the calculation of weights. This varies as does the 
shrinkage allowance on patterns, with the composition of prod- 
uct. The specific gravity of malleable, that is, the ratio of its 
density to that of water is between 7.25 and 7.45 and de- 
pends on the temperature at which the experiment is made. 
The metal made to pass the specifications of the American 
Society of Testing Materials will have a specific gravity of 
about 7.40. The "shrinkage allowance" referred to under such 
circumstances should be about 0.9 to 1 per cent, agreeing rather 
well with the usual ^-inch per foot used by patternmakers. 
It should be noted in passing that the differences in "shrink- 
age" between metal differing in carbon content is actually an- 
nealing. 

All white cast iron shrinks very nearly the same amount 
in cooling from the molten state (*4-inch per foot) but iron 
high in carbon increases in size more when the carbon is lib- 
erated than those low in that element. 



Selected Bibliography 

I GENERAL INFORMATION 

Chronology of -Iron and Steel, by Stephen L. Goodale, Pittsburgh Iron & 
Steel Foundries Co. (1920.) 

A chronology of important discoveries, developments, etc., in iron and 
steel industry dating from prehistoric times to 1919. 294 pages. 

Pcnton's Foundry List; published by The Penton Publishing Go., Cleve- 
land. (1922.) 

A list of all of the foundries in the United States and Canada, 
arranged by class of products. A separate list of malleable iron 
foundries is included. 896 pages. 

The Romance of Modern Manufacture, by Charles R. Gibson; published 
by Seeley & Co., Ltd. 

A popular account of the marvels oir manufacturing. Malleable iron 
is included. 320 pages, illustrated. 

Index of the Transactions of the American Foundrymen's Association; 
American Foundrymen's Association, Chicago. (1921.) 
An index of all volumes of Transactions from IX to XXIX inclusive, 
containing hundreds of references to articles on malleable iron. An 
author's . index also is given. 192 pages. 

Foundrymen's Handbook; published by the Penton Publishing Co. (1922.) 
Contains data on malleable iron, as well as on all other branches of 
the foundry industry. 309 pages. 

Iron and Steel, by J. H. Stansbie ; published by ^Constable & Co., Ltd. 
(1915.) 

This book is a comprehensive treatise on the modern aspects of iron 
and steel manufacture together with an account of its history. Mal- 
leable castings are included in the text. 375 pages, illustrated. 

The Founder's Manual, by David W. Payne; published by D. Van Nos- 
trand Co., New York. (1920.) 

A handbook for foundrymen, with tables on mathematics, weights and 
measures, materials, alloys, foundry fuels, cupola practice, sand, 
molding practice, etc. One brief chapter is devoted exclusively to mal- 
leable cast iron. 676 pages, 245 illustrations, and list of coke and 
anthracite pig irons by trade names. 

Foundry Cost Accounting, by Robert E. Belt; published by the Penton 
Publishing Co. (1919.) 

The twelve chapters cover every phase of accurate cost methods 
and their various application to different branches of the foundry 
industry. The principles and forms used, the classification of accounts, 



386 Selected Bibliography 



the methods of distributing overhead expenses, the procedures used to 
determine the cost of individual jobs or classes of work, are such that 
they can be easily adopted to fit the requirements of any foundry 
gray iron, malleable, steel or nonferrous. 262 pages, 75 forms and 
charts. 



Co-operation Between the Engineer and the Malleable Iron Foundry, by 
G. F. Meehan. 

A discussion of the need of teamwork between engineers and mal- 
leable foundrymen to insure better design of castings. 1000 words. 
Transactions, A. F. A., Vol. XXV, p. 221. 

The Commercial Side of the Malleable Iron Industry, by W. G. Kranz. 
A brief historical sketch of the industry, followed by an account of 
recent developments (1916) and a statement covering erroneous con- 
ceptions of the properties of malleable that are being corrected. 
1000 words. Transactions, A. F. A., Vol. XXV, p. 501. 

British and American Malleable Cast Iron, by T. Turner. 

Theory and practice are discussed and futures of industries in Eng- 
land and the United States are predicted. Iron Age, Vol. 102, p. 970. 

Improvements in Making Malleable Iron. 

A review of recent progress (1919) based on research and develop- 
ment work of American Malleable Castings association. Raw Mate- 
rials, Vol. 1 (1919), p. 443-8. 

II PRODUCTION 

The A B C of Iron and Steel, edited by A. O. Backert; published by the 
Penton Publishing Co., Cleveland. (1921.) 

Twenty-six chapters by eminent authorities covering manufacture of 
iron and steel from mine to finished product. Contains chapters on 
making gray iron, steel and malleable castings, the latter product being 
covered by H. A. Schwartz. 408 pages, 269 illustrations, numerous 
statistical tables and index. 

The Production of Malleable Castings, by Richard Moldenke. (1910.) 
(Out -of print.) 

The first book published covering the production of malleable, includ- 
ing history, characteristics of malleable, testing, patternmaking, mold- 
ing, melting, equipment, casting, annealing and cost of malleable. 
125 pages, 35 illustrations. 

International Library of Technology; published by International Text- 
book Co. 

Volume on "the manufacture of gas, iron, steel and cement." Con- 
tains information on malleable iron. 

Non-Technical Chats on Iron and Steel, by L. W. Spring; F. Stokes Co. 
(1917.) 
A review, in popular manner, of methods of producing iron and 



Selected Bibliography 387 

steel products, with a reference to the making of malleable cast iron. 

Malleable Cast Iron, by S. J. Parsons; Constable & Co., Ltd. (Tem- 
porarily out of print.) Reprinting. 

Melting, molding, annealing and cleaning operations are explained ; 
equipment is described, and principles of design and method of making 
patterns discussed. 182 pages, 86 illustrations. 

Iron and Steel, Vol. I, by William Henry Greenwood; Henry Carey Baird 

& Co. I -jifi 

Refractory materials, iron ores, metallurgical chemistry of iron, pig 
iron, blast furnace operation, malleable cast iron, production of mal- 
leable in open hearth. 255 pages, illustrated. 

Notes on Foundry Practice, by J. J. Morgan; published by Charles Grif- 
fin & Co., Ltd. (1912.) 

This work gives a general description of the methods of founding 
and provides condensed and reliable information as to the material 
used and its methods followed in more particularly iron founding. 
The subject of malleable castings is included. 104 pages, 24 illus- 
trations. 

International Library of Technology; published by International Text- 
book Co. 

Volume on "machine molding, foundry appliances, malleable castings, 
etc." Contains a complete chapter of 36 pages on the properties and 
composition of malleable cast iron. 

General Foundry Practice, by William Roxburgh; Constable & Co., Ltd. 
(1919.) 

A treatise on general iron founding with notes on metallurgy, melt- 
ing, molding, heat treatment, cleaning, etc. Malleable castings are 
mentioned. 308 pages, 161 illustrations. 

General Foundry Practice, by A. McWilliam and Percy Longmuir ; Chas. 
Griffin & Co., Ltd. (1920.) 

Molding sands, foundry equipment, refractories, mixing, pouring, heat 
treatment, testing, etc., as applied to general foundry work. Reference 
is made to malleable cast iron. 384 pages illustrated. 



Malleable Cast Iron, by Bradley Stoiighton. 

A brief outline of the methods of manufacture and properties of mal- 
leable cast iron, as known in 1908. School of Mines Quarterly 
(Columbia Univ.), Vol. 29, p. 54. 

The Production of Malleable Castings, by Richard Moldenke. 

A brief treatise including history of the industry, properties of mal- 
leable, metallurigcal principles, and methods of production. 4500 
words. An address before Connecticut Valley Section of the Amer- 
ican Chemical Society, Jan. 4, 1913. Transactions, A. F. A., Vol. 21, 
p. 815. 



388 Selected Bibliography 



Some of the Factors in the Manufacture of High Grade Malleable Cast- 
ings, by J. G. Garrard. 

A brief discussion of the difficulties in making malleable castings of 
heavy section. Results of iron produced by practically eliminating top 
blast are given. 800 words. Transactions, A. F. A., Vol. XXVII, 
p. 370. 

Malleable Iron Its Manufacture, Characteristics and Uses, by J. P. Pero. 
Development of the industry, method of melting, distinction between 
shrinkage and contraction, annealing practice and specifications are 
the principal topics covered in this paper. 3600 words. Transactions, 
A. F. A, Vol. XXIII, p. 451. 

An Outline to Illustrate the Inter-dependent Relationship of the Variable 
Factors in Malleable Iron Production, by L. E. Gilmore. 
A discussion of the chemical analysis and miscrostructure of white 
iron, types of furnaces employed, quality of fuel, control of combus- 
tion, ideal mixtures, heat-treating and annealing, etc. 2800 words 
and one control chart of operations. Transactions, A. F. A., Vol. 
XXIVi p. 233. 

Progress in Manufacture of Malleable Iron, by Enrique Touceda. 

A progress report of recent advances in the technical development of 
the malleable industry as of 1920, with a discussion of future possi- 
bilities. Furnace design and melting practice, and improved prop- 
erties of product are discussed. 4500 words. Transactions, A. F. A., 
Vol. XXIX, p. 354. 

Fuel and Materials 

Burning Liquid Fuel, by W. N. Best ; published by U. P. C. Book Co., 
Inc. (1922.) 

History, theory and applications of oil fuel in 28 chapters, one of 
which (3500 words, 17 illustrations) is devoted to malleable iron, 
gray iron and brass foundry practice. 341 pages, 316 illustrations. 

Foundry Irons, by Edward Kirk; Henry Carey Baird & Co. (Out 
of print.) 

History of ironmaking, pig iron production, mixing irons, casting by 
direct process, foundry chemistry, analysis, etc., as applied to cast iron 
and malleable cast iron. Three chapters are devoted to malleable. 276 
pages ; illustrated. 

Blast Furnace and the Manufacture of Pig Iron, by Robert Forsythe ; 
published by the U. U. C. Book Co. (1922.) 

An elementary treatise for the use of the metallurgical students and 
the furnaceman. Several pages are devoted to malleable pig iron, 
castings and specifications. 368 pages. 



Fuel and Combustion, by Max Sklovsky. 

A general . article on economy of combustion which in conclusion 



Selected Bibliography 389 

touches on tunnel kilns for annealing malleable iron castings. 2500 
words, 9 illustrations. Transactions, A. F. A., Vol. XXIX, p. 367. 
Coal Its Origin and Use in the Air Furnace, by F. Van O'Linda. 

The properties of coal for air furnace melting are described and 
suggestions for firing given. Cost per .B.t.u. is stated. 1600 words. 
Transactions, A. F. A., Vol. XXIV, p. 251. 

Pulverized Coal for Melting Malleable Iron, by W. R. Bean. 

An explanation of the factors controlling the use of powdered coal 
in malleable melting. Foundry, Vol. 45, p. 487. 

Powdered Coal as a Fuel in the Foundry, by A. J. Grindle. 

Uses in the foundry, problems of feeding and burning, carburization, 
economy, kind of coal to use, preparing fuel, and cost, are the 
principal topics discussed. 4000 words. Transactions, A. F. A., Vol. 
XXVIII, p. 303. 

Efficient Use of Pulverized Coal in Malleable Foundry Practice, by 
Milton W. Arrowood. 

The author discusses methods of preparing pulverized fuel, mixing 
it with the air, introducing it into the furnace, and controlling furnace 
conditions. The theory of combustion receives considerable attention. 
8400 words, 9 illustrations. Transactions, A. F. A., Vol. XXVIII, 
p. 277. 

Plant and Equipment 

Foundry Molding Machines and Pattern Equipment, by Edwin S. Carman; 
published by the Penton Publishing Co., Cleveland. (1920.) 
A treatise showing the use- of molding machines in all types of 
foundries. Parts of the book are of particular interest to malleable 
foundrymen. 225 pages, 220 illustrations. 

Electric Furnaces in the Iron and Steel Industry, by Rodenhauser- 
Schoenawa-Von Baur; published by John Wiley & Sons. (1920.) 
This book answers clearly and untechnically every question that may 
arise in the electric steel industry. Malleable iron is included. 460 
pages, 133 illustrations. 

A Study of the Malleable Furnace, by Harbison-Walker Refractories Co. 
98 pages, illustrated. 



A Continuous Malleable Foundry. 

An illustrated description of the new (1911) foundry of the Crane 
Co., Chicago. Foundry, Vol. 38, p. 1. 

Making Large Castings from Air Furnace Iron, by H. E. Diller. 

A description of a foundry of the Westinghouse company equipped 
with two 40 and one 15-ton air furnaces. Foundry Vol 48 (1920) 
p. 973-77. 

A New Annealing Furnace. 

Description of malleable annealing furnace operated by the Arcade 



390 Selected Bibliography 



Malleable Iron Co. Foundry, Vol. 48 (1920), p. 769-71. 

Foundry Plant and Machinery, by J. Horner. 

A chapter of a series. This chapter is devoted to the equipment and 
practice in malleable foundries. Engineering, Vol. 90, pp. 787-91. 

Annealing Furnaces, by George Rietkolter. 

A description, with drawings, of malleable annealing furnaces. Stahl 
und Risen, Vol. 27 (1908), p. 1652. 

Malleable Cast Iron and the Open-Hearth Furnace, by G. A. Blume. 

A description of two open-hearths built in a malleable plant in Fin- 
land in 1910-11. The operation is discussed in detail. 8000 words, 
3 illustrations. Transactions, A. F. A., Vol. 21, p. 431. 

How an Oil Fired Malleable Furnace Operates. 

A description of an oil fired air furnace with data on consumption, 
costs, etc. Foundry, Vol. 45, p. 503. 

The 25-Ton Air Furnace, by F. C. Rutz. 

A brief description of a 25-ton furnace, with dimensions, operating 
expense, melting ratio, flexibility of operation, etc. 800 words. Trans- 
actions, A. F. A., Vol. XXV, p. 522. 

The Waste Heat Boiler for Malleable Furnaces. 

The author believes waste heat installations in the foundry will be 
justified by results. Foundry, Vol. 46, p. 220. 

The Theory of the Modern Waste-Heat Boiler and the Possible Applica- 
tion of Such Boilers to Malleable Melting Furnaces, by Arthur D. 
Pratt. 

An explanation of the theory of the waste heat boiler and a descrip- 
tion of the installation of one attached to an air furnace at the Mc- 
Cormick works of the International Harvester Co. The performance 
of this boiler is given and results tabulated. 600 words, 6 drawings 
and charts. Transactions, A. F. A., Vol. XXVI, p. 349. 

Pointers from the -Practice of a Malleable Iron Foundry. 

A description of the installation of waste heat boilers on air furnaces 
at the plant of the Buhl Malleable Co., Detroit (1909), 1500 words, 
11 illustrations. Castings, Vol. Ill, p. 196. 

A Modern Coreroom, by Donald S. Barrows. 

A description of the coreroom built in 1918 at the malleable plant 
of the T. H. Symington Co., Rochester, N. Y. 2000 jyords, 10 illus- 
trations. Transactions, A. F. A., Vol. XXVII, p. '429. 

A New Research Department for a Large Malleable Plant, by H. A. 
Schwartz. 

A description of the laboratory built in 1919-20 by the National Mal- 
leable Castings Co., Cleveland. The laboratory is for the research 
requirements of a group of scattered foundries and the article lists 
and describes the apparatus and outlines the arrangement of depart- 



Selected Bibliography 391 

ments. 3700 words, 4 illustrations. Transactions, A. F. A., Vol. 
XXIX, p. 380. 

Early Laboratories in Malleable Industry. 

Discussion by Richard Moldenke and H. A. Schwartz of the pioneer 
laboratories of 1891 to 1903, with reference to the work of Dr. 
Moldenke, H. E. Diller, A. A. Pope and others. 1200 words. 
Transactions, A. F. A., Vol. XXVII, p. 400. 

Melting Practice 

Calculating Mixtures for Malleable Cast Iron, by Harrold Hemenway. 
A system of calculating mixtures is fully explained and the impor- 
tance of the various constituents emphasized. 8000 words, 27 tables. 
Transactions, A. F. A., Vol. XXIII, p. 413. 

Influence of Changing the Composition of Malleable Castings, by P. 
Rodigin. 

Results of tests showing effects of additions of manganese, silicon, 
aluminum, titanium, antimony and tin, copper, bismuth and lead, 
sulphur and phosphorus to malleable. 1000 words. Transactions, A. 
F. A, Vol. XXII, p. 201. 

Malleable Troubles, by Richard Moldenke. 

A discussion of melting problems, particularly those related to the 
selection of iron, use of scrap, etc. Annealing also is discussed. 
3500 words. Transactions, A. F. A., Vol. XXII, p. 251. 

Effect of Varying Silicon and Carbon in Malleable Iron Mixtures, by 
A. L. Pollard. 

A discussion based on records of analyses and tests covering a period 
of 8 months, during which time the silicon and carbon contents were 
varied. 1200 words. Transactions, A. F. A., Vol. XXIII, p. 437. 

Titanium for Malleable Iron, by C. H. Gale. 

Ferro-titanium was added to malleable- in the ladle and tests of the 
resulting product made. The paper is a discussion of the results. 
2400 words, 5 tables. Transactions, A. F. A., Vol. 20, p. 271. 

Malleable Castings by a New Process (1908), by E. C. Origley. 

Wrought iron and soft steel are melted in a crucible, the metal is 
quieted by additions, and poured. Iron Age, Vol. 81, p. 1312-13. 

Standardization of Air Furnace Practice, by A. L. Pollard. 

A discussion of design, touching on length of hearth, depth of bath, 
length of firebox, height of roof, opening at neck and wall thick- 
nesses. Advantages and disadvantages are compared and notes on 
operation presented. 1800 words. Transactions, A. F. A., Vol. 
XXIV, p. 245. 

Melting in an Air Furnace with Fuel Oil, by J. P. Pero. 

Disadvantages are compared with advantages, and data on oil-operated 



392 Selected, Bibliography 



air furnaces in three plants are given in parallel. 2000 words, 1 table. 
Transactions, A. F. A., Vol. XXVIII, p. 316. 

The Equipment of Air Furnaces Using Oil as Fuel, by W. N. Best. 

Method of changing air furnace from coal firing to oil firing, with 
suggestions regarding design of burners and method of operation. 
1500 words. Transactions, A. F. A., Vol. XX, p. 421. 

The Application of Pulverized Coal to Malleable Melting Furnaces, by 
Joseph Harrington. 

The author discusses factors affecting successful use of pulverized 
coal in air furnaces, covering rapidity of heating, temperature, effect 
on furnace lining, amount of carbon burned out, etc. 2600 words. 
Transactions, A. F. A, Vol. XXVI, p. 394. 

Application of Pulverized Coal to the Air Furnace, by W. R. Bean. 

A discussion of the disadvantages of hand firing and of the possi- 
bilities of overcoming some of them by using pulverized coal. Meth- 
ods of altering air furnaces for this fuel and results of tests are 
given. 2800 words. Transactions, A. F. A., Vol. XXVI, p. 337. 

The Triplex Process of Making Electric Furnace Malleable, by H. A. 
Schwartz. 

A complete description of the triplex process invented by W. G. 
Kranz and employed by -the National Malleable Castings Co. This 
process involves the use of the cupola, converter and electric furnace. 
3200 words, 5 illustrations. Transactions, A. F. A., Vol. XXIX, 
p. 342. 

The Refining of Cupola Malleable Iron in the Electric Furnace, by A. W. 
Merrick. 

The advantages of cupola melting of malleable are recounted, and the 
results of experiments in refining the cupola metal electrically are 
presented and discussed. 2400 words, 3 illustrations. Transactions, 
A. F. A, Vol. XXVIII,. p. 322. 

Molding 

Foundry Work, by Burton L. Gray ; published by the American Technical 
Society. (1920.) 

A practical handbook on standard foundry practice, including hand 
and machine molding, cast iron, malleable iron, steel and brass cast- 
ing, foundry managements, etc. 224 pages, 191 illustrations. 



The Control of Chill in Cast Iron, by G. M. Thrasher. 

Bulletin, A. I. M. E. (1915), p. 2129. 
Malleable Cast Iron, by F. Erbreich. 

Methods of molding and annealing are described and illustrated. 

Stahl und Eisen, Vol. 35, pp. 549-53, 652-58, 773-81. 
Producing Machinable Malleable Iron Castings, by A. T. Jeflfery. 

The author explains how to avoid common machining difficulties by 



Selected Bibliography 393 

adopting good foundry practice. Foundry, Vol. 45, p. 449. 

Gating Malleable Iron Castings, by A. M. Fulton. 

Methods of properly gating malleable castings with various typical sec- 
tions, avoiding chills wherever possible. Shrinkage defects are dis- 
cussed. 2100 words, 9 illustrations. Transactions, A. F. A., Vol. 
XXV, p. 239. 

Annealing 

A Study of the Annealing Process for Malleable Castings, by E. L. 
Leasman. 

A review of the metallography of white cast iron is followed by a 
description of tests to study the effects of different packing materials, 
of different annealing temperatures, of different times of annealing 
and different rates of cooling. 3200 words, data on 23 experiments, 
15 micrographs. Transactions, A. F. A., Vol. XXII, p. 169. 

Experiments in Annealing Malleable Iron, by H. E. Diller. 

The author discusses the two actions occurring in the anneal, and 
describes tests made to ascertain proper temperatures, time, rate of 
cooling, etc. 3000 words, 4 illustrations. Transactions, A. F. A., 
Vol. XXVII, p. 404. 

Continuous Tunnel Annealing, by Philip d'H. Dressier. 

A description of the Dressier type tunnel annealing furnace for 
malleable castings, on the basis of its development in 1918. 2400 
words, 5 illustrations. Transactions, A. F. A., Vol. XXVII, p. 414. 

The Application of Powdered Coal to Malleable Annealing Furnaces, by 
Charles Longnecker. 

Following a brief historical sketch of the subject, the author describes 
the installation at the plant of the Pressed Steel Car Co., comparing 
results with those obtained by the use of natural gas and fuel oil. 
2100 words, 3 illustrations. Transactions, A. F. A., Vol. XXVIII, 
p. 270. 

Effects of Annealing Gray and Malleable Iron Bars in Copper Oxide 
Packing, by H. E. Diller. 

Malleable iron bars were packed in black oxide of copper and annealed 
in an experimental furnace. In one case the copper soaked through, 
the bar analyzing 21.4 per cent copper. Similar tests at various 
annealing temperatures are described. 1600 words, 8 illustrations. 
Transactions, A. F. A., Vol. XXVIII, p. 261. 

Malleable Annealing Experiments, by S. B. Chadsey. 

Results of tests of malleable subjected to repeated annealing. Foundry, 
Vol. 37, p. 215. 

Reducing the Malleable Iron Annealing Period, by A. E. White and R. S. 
Archer. 
Time can be saved by raising the annealing temperature slightly above 



394 Selected Bibliography 

the critical point and maintaining it at 700 degrees long enough to 
change 0.70 per cent combined carbon to graphitic carbon. Foundry, 
Vol. 47, p. 61. 

Graphitization of White Cast Iron upon Annealing, by Paul D. Merica and 
Louis J. Gurevich. 

A description and discussion of experiments in which the graphitiza- 
tion ranges of temperatures for three compositions for car wheels 
were determined. Light is thrown on certain moot questions of the 
metallurgy of annealing. 2400 words, 7 illustrations. Transactions, 
A. I. M. M. E., Vol. LXII, p. 509. 

The Annealing of Malleable Castings, by A. E. White and R. S. Archer. 
Following a discussion of the constituents of malleable castings, the 
authors describe experiments with white iron, covering the time of 
annealing, the temperature and method of treatment. In conclusion, 
the authors state an ideal heating cycle is impossible, each case depend- 
ing on local requirements. Transactions, A. F. A., Vol. 27, p. 351. 

Researches in the Annealing Process for Malleable Castings, by Oliver 
W. Storey. 

A discussion of research work on packing materials, temperature of 
annealing, time of annealing, and rate of cooling, with important con- 
clusions. 4400 words, 10 micrographs. Transactions, A. F. A., Vol. 
XXIII, p. 460. 

Copper Diffuses Through Cast Iron, by H. E. Diller. 

An investigating effect of oxidizing packings in annealing malleable, it 
was found that copper penetrated bar packed in copper oxide. Foundry, 
Vol. 47 (1919), p. 779-80. 

Production of Malleable Castings, by Richard Moldenke. 

An extensive discussion of the principles of annealing, with data 
on operation and description of apparatus. The Iron Trade Review, 
Vol. 44 (1910), pp. 540, 776. 

Notes on Malleable Cast Iron, by R. Namias. 

A discussion of composition of metal, rate of cooling during anneal, 
etc. Engineering, Vol. 88, p. 669. 

Finishing 

Oxy-Acetylene Welding Manual, by Lorn Campbell, Jr., John Wiley & 
Sons, Inc. 

Apparatus and methods of oxy-acetylene welding of various materials, 
including malleable. Glossary of welding terms. 

Oxy-Acetylene Welding Practice, by Robert J. Kehl, published by Amer- 
ican Technical Society. 

A practical presentation of the modern processes of welding, cutting 
and lead burning with special attention to welding technique of 
different metals. Simple and complex cases of expansion and con- 



Selected Bibliography 395 

struction preheating steel, cast iron, malleable iron, aluminum, cop- 
per, brass and bronze welding. 110 pages, 117 illustrations, diagrams 
and tables. 

Oxy- Acetylene Welding, by S. W. Miller ; Industrial Press. 

Twelve chapters on oxy -acetylene welding of various materials, in- 
cluding malleable cast iron. 287 pages, 192 illustrations. 

Troubles Encountered in Machining Malleable Iron: Causes and Reme- 
dies, by A. T. Jeffery. 

A discussion of machining difficulties due to pure hard white iron, 
under-annealed iron, iron cooled too quickly, burned iron, and "tough 
and stringy" iron. The use of test lugs, effect of low silicon, etc., 
are considered and in summary, the author urges co-operation between 
founder and user of castings. 2400 words, 7 illustrations. Transac- 
tions, A. F. A, Vol. XXVI, p. 383. 



Ill METALLURGY AND METALLOGRAPHY 

The Chemical and Metallographic Examination of Iron, Steel and Brass, 
by Hall and Williams; published by McGraw-Hill Book Co. (1921.) 
Malleable iron is included in the volume. 500 pages, illustrated. 

Cementation of Iron and Steel, by Frederico Giolitti ; published by Mc- 
Graw-Hill Book Co. (1915.) 

Information on the theory of malleablized castings. 407 pages, illus- 
trated. 

Cast Iron in the Light of Recent Research, by William H. Hatfield; 
Charles Griffin & Co., Ltd. 

The iron-carbon alloys and cast iron from the standpoint of the 
equilibrium diagram, with chapters on the influences of silicon, phos- 
phorus, sulphur, manganese, etc. Malleable iron is given considerable 
attention, the heat treatment of white iron, influence of sulphur on 
the stability of iron carbide in the presence of silicon, and the phos- 
phorus content permissible in malleable being discussed. Mechanical 
properties of malleable are outlined. 292 pages, 199 illustrations. 

An Outline of the Metallurgy of Iron and Steel, by A. H. Sexton and 
J. S. G. Primrose; Scientific Publishing Co. 

An outline of processes of iron and steelmaking, with a discussion of 
metallurgy involved. Malleable iron is included. 587 pages, 271 illus- 
trations. 

An Elementary Textbook of Metallurgy, by A. Humbolt Sexton; pub- 
lished by Charles Griffin & Co., Ltd. 

This work is intended for the use of students, both for those com- 
mencing the study of metallurgy and those who are already engaged 
in metallurgical industries and who desire some knowledge of the 
principles on which the processes they are using are based. Mai- 



396 Selected Bibliography 



leable iron is taken up in Part I under metallurgical processes. 263 
pages, 71 illustrations. 

Principles of Metallography, by Robert S. Williams; published by Mc- 
Graw-Hill Book Co. (1920.) 
Malleablizing is included in this text. 158 pages. 

Practical Metallography of Iron and Steel, by John S. G, Primrose; 
published by Scientific Publishing Co. 
Contains information on malleable cast iron. 129 pages, illustrated. 

Methods of Chemical Analysis and Foundry Chemistry, by Frank L. 
Crobaugh; Penton Publishing Co. (1910.) 

Sampling and preparation of samples; determination of iron, phos- 
phorus, sulphur, etc.; analysis, etc., as applied to white and chilled 
castings, malleable castings, gray iron castings, etc. 110 pages. 

The Metallurgy of Iron and Steel, by Bradley Stoughton ; McGraw-Hill 
Book Co. "(1913.) 

Iron and carbon, manufacture of pig iron, bessemer process, open- 
hearth process, defects in ingots and castings, treatment of steel, iron 
and steel founding, constitution of cast iron, malleable cast iron, intro- 
duction to metallurgy, etc. 539 pages, illustrated. 

Metallurgy of Iron and Steel, by A. Humbold Sexton ; published by Scien- 
tific Publishing Co. 

This book covers in one volume the whole field of metallurgy of iron 
and steel. Method of making malleable iron is described. 600 pages, 
270 illustrations. 

Metallurgy of Iron, by Thomas Turner ; published by Charles Griffin & 
Co, Ltd. (1920.) 

Contains information on the production of malleable cast iron. 486 
pages, illustrated. 

The Metallography of Steel and Cast Iron, by Henry Marion Howe; 
McGraw-Hill Book Co., New York. (1916.) 

A finished treatise on general metallography, with numerous references 
to malleable iron. 641 pages, hundreds of illustrations, numerous 
tables and diagrams, and complete indices. 

The Metallography and Heat Treatment of Iron and Steel, by Albert 
Sauveur; Sauveur and Boylston, Cambridge, Mass. (1916.) 
A thorough study of metallography covering all types of iron and 
steel. One chapter is devoted exclusively to malleable cast iron, and 
several others are pertinent to malleable producers and users. 486 
pages, 437 illustrations. 

Metallography Applied to Siderurgic Products, by Humbert Savoia; pub- 
lished by E. & F. N; Spon, Ltd. 

A complete chapter of 23 pages is devoted to malleable cast iron. 180 
pages, illustrated. 



Selected Bibliography 397 

Metallography, by Arthur H. Hiorus ; published by Macmillan & Co. 
(1902.) 

An introduction to the study of the structure of metals chiefly by the 
aid of the microscope. Several pages are given over to malleable cast 
iron. 158 pages, illustrated. 

Iron and Steel, by O. F. Hudson; Constable & Co., Ltd. 

An introductory textbook for engineers and metallurgists. Methods of 
production are not covered in this book. Metallurgy of malleable cast 
iron is discussed briefly. 184 pages, 47 illustrations. 



Fractures and Microstructures of American Malleable Cast Iron, by W. R. 
Bean, H. W. Highriter and E. S. Davenport. 

A discussion of typical specimens of malleable cast iron based on 
chemical, miscroscopic and mechanical examination. 6500 words, 40 
illustrations. Transactions, A. F. A., Vol. XXIX, p. 306. 

Some Remarks Regarding the Permissible Phosphorus Limit in Malleable 
Iron Castings, by Enrique Touceda. 

Dynamic tests of malleable containing .181, .252, .325 and .388 per 
cent phosphorus were made, and the author interprets the results for 
the guidance of malleable foundrymen. 3500 words, 5 illustrations, 2 
tables. Transactions, A. F. A., Vol. XXIV, p. 209. 

Report on Methods of Etching Malleable Iron for Visual Investigation of 
Structure, by E. Heyn. 

The author recommends a solution of 1 gram of copper-ammonium 
chloride in 12 grams of water. Etching requires a minute. 1500 
words, 8 illustrations. International Association of Testing Materials, 
Brussels, 1906. 

Change of Structure in Iron and Steel, by William Campbell. 

Review of iron-carbon equilibrium diagram, illustrated by photomi- 
crographs of irons and steels. Journal, Franklin institute, Vol. 163, 
pp. 407-34. 

Constitution of the Iron-Carbon Alloys. 

A discussion of Sauveur's article in Journal of Iron and Steel insti- 
tute by Benedicts, who upholds Roozeboom's application of phase rule. 
Also discussed by Howe, Stansfeld, Stead and others. Mctallurgie, 
Vol. 4, pp. 216-41. 

Influence of Silicon upon the Iron-Carbon System. 

Author determines amount of carbon remaining in solution after 
adding definite amounts of silicon to molten pig iron. Influence of 
silicon upon solidification point also determined. Stahl und Eiscn, 
Vol. 27, 482-87. 

Note on the Liquids in the Iron-Carbon Diagram, by G. Cesaro. 

Discussion of an attempt to determine the course of the curve joining 
the points at which molten iron-carbon alloys begin to solidify. Jour- 
nal, Iron and Steel Institute. (1919.) 



398 Selected Bibliography 



The Alloys of Iron and of Carbon, by Georges Charpy. 

A lecture on the iron-carbon system, in which the author reviews the 
knowledge of the subject as of 1909. Bulletin de la Socicte Chimique 
de France, Vol. 3, p. i-xlvi. 

Some Iron-Silicon-Carbon Alloys, by W. Gontermann. 

A review of binary systems contributing to the above equilibrium, 
with the author's theory on the Fe-C system. Zeitschrift fur anor- 
gische Chemie. Vol. 59 (1909), p. 373-414. 

Development of the Fusion Diagram of Iron-Carbon Alloys, by F. Wust 
An explanation of the theory underlying the construction of the fusion 
diagram. The author proposes the term "Ledeburite." Zeitschrift 
fur Elektrochimie, Vol. 15 (1910), p. 565-584. 

Chemical Equilibrium in the Reduction and Cementation of Iron, by Ru- 
dolph Schenck. 

Zeitschrift fur Elektrochimie, Vol. 21 (1915), p. 37; Vol. 22 (1916), 
p. 121; Vol. 24 (1918), p. 248. 

Separation of Graphite in White Cast Iron Heated under Pressure, by 
Georges Charpy. 

Change of carbide to graphite when the metal is subjected to high 
pressure and a temperature of from 700 to 1000 degrees. Cotnptes 
Rendus, Vol. 148 (1909), p. 1767. 

The Stable System: Iron-Carbon, by Rudolf Ruer and Nikolaus Iljin. 
A thorough discussion covering the solubility of carbon in solid iron 
and the separation of temper carbon. Metallurgie, Vol. 8, p. 97. 

The System Iron-Carbon, by A. Baikov. 

A study of the solidification of iron showing that separation of 
graphite and cementite follows the same line on the diagram. Revue 
de Metallurgie, Vol. 8, p. 315. 

The Solubility of Carbon in Iron, by O. Ruff and O. Goecke. 

A discussion attending the determination of the solubility of carbon 
in iron at temperatures between 1200 and 2600 degrees Cent. Metal- 
lurgie, Vol. 8, p. 417. 

The Equilibrium Diagram of Iron-Carbon Alloys, by Otto Ruff. 
Metallurgie, Vol. 8, pp. 456-64, 497-508. 

A Study of the Annealing Process for Malleable Castings, by Oliver W. 
Storey. 

The effects of packing material, temperature of annealing, time of 
annealing and rate of cooling are studied. A thorough and original 
discussion on annealing. Metallurgical and Chemical Engineering, 
Vol. 12, p. 383. 

The Nature of the A 2 Transformation in Iron, by K. Honda. 

A study of recent investigations. Scientific Reports, Tohoku Imperial 
University, Vol. 4 (1915), p. 169. 



Selected Bibliography 399 

Phosphorus Limit in Malleable Castings, by Enrique Touceda. 

The author describes tests which showed that when combined carbon 
was low, evil effects of phosphorus were slow to make themselves 
felt. Iron Age, Vol. 96, p. 92. 

Sulphur in Malleable Cast Iron, by R. H. Smith. 

The author concludes that sulphur is not removed in the annealing, 
process and does not appear to have evil effects below 0.15 per cent. 
Journal, Iron and Steel Institute. Vol. 92, p. 141. 

Recrystallization after Plastic Deformation, by H. M. Howe. 
Bulletin, A. I. M. E. (1916), p. 1851-60. 

Decarburization of Iron-Carbon Alloys, by W. H. Hatfield. 

The author opposes theory that carbon must be in the form of temper 
carbon before it can be removed by oxidation. Engineering., Vol. 87 
(1910), p. 801. 

Graphitization of Iron-Carbon Alloys, by Kotaro Honda and Takejiro 
Murakanu. 

In pure iron carbon alloys, graphitization is caused by the decom- 
position of the cementite solidified during cooling from the melt. 
Journal, Iron and Steel Institute (Sept.). (1920.) 

Graphitizing of White Cast Iron, by R. S. Archer. 

The author draws conclusions regarding the initiation of graphitiza- 
tion below the A point and completion near or at that point. Foundry, 
Vol. 48 (1920), p. 192-4. 

Concerning the Solubility of Graphite in Iron, by Carl Benedicts. 

Tests show that graphite is appreciably soluble in ferrite at 940 
degrees Cent., therefore, iron-carbon diagram should be drawn as pro- 
posed by LeChatelier, Stansfield and Charpy. Metallurgie, Vol. 5 
(1908), p. 41-45. 

Influence of Phosphorus on the Iron-Carbon System, by F. Wust. 

The subject is brought up to date (1908) and results of tests and 
experiments are given. Metallurgie, Vol. 5, p. 73-87. 

The Nature of the Cast Irons, by G. B. Upton. 

Discussion of Fe-C diagram, relating particularly to liquidus and 
solidus lines. Journal of Physical Chemistry, Vol. 13 (1909), p. 
388-416. 

The Effect of Foreign Substances Upon the Fusion Diagram of Iron- 
Carbon Alloys, by P. Goerens. 

An investigation of the iron-manganese-carbon and iron-phosphorus- 
carbon systems. Metallurgie, Vol. 6 (1910), p. 537-50. 

Theory of Malleablizing, by W. H. Hatfield. 

The European and American methods of making malleable castings 
are described. From a lecture before Institution of Engineers and 
Shipbuilders of Scotland. Foundry, Vol. 36, p. 30. 



400 Selected Bibliography 



Graphitization in Iron-Carbon Alloys, by Kunlichi Tawara and G. Ashara. 
Twenty-seven iron-carbon alloys were melted and after slight cooling 
cast into molds and cooled at varying rates. Deductions from these 
tests are discussed. Journal, Iron and Steel Institute (1919). 

The Theory of Annealing, by F. Wust. 

A discussion of the metallurgy of annealing with special reference to 
the migration of carbon. Metallurgie, Vol. 5 (1908), p. 7-12. 

The Evolution of the Malleable Iron Process, by J. P. Pero and J. C. 
Nulsen. 

An account of the advance in metallurgy of malleable practice, touch- 
ing upon the importance of sulphur and phosphorus, "steely" iron, 
uses of the microscope, value of strength tests, fatigue failure, and 
properties of malleable. 4000 words. Transactions, A. F. A., Vol. 
XXV, p. 222. 

What Is the Normal Fracture of Good Malleable Iron? by Enrique 
Touceda. 

The author explains how the test lug should be secured and describes 
the appearance of various fractures, interpreting the significance of 
each. 2000 words, 6 illustrations. Transactions, A. F. A., Vol. XXV, 
p. 506. 

Judging Malleable by Fracture, by Richard Moldenke. 

Photographs of typical fractures, with suitable explanation of each. 
Foundry, Vol. 37, p. 237. 

IV PROPERTIES AND USES 

Materials of Construction, by Adelbert P. Mills ; published by John Wiley 
& Sons, Inc., New York. (1922.) 

Manufacture and uses of cements, clay products, ferrous and non- 
ferrous metals, timber, rope and mechanical fabrics. One chapter 
(2500 words), devoted to malleable cast iron, describes methods of 
production and lists properties and uses. 

Materials of Construction, by M. O. Withey and James Aston ; John Wiley 
& Sons, Inc. (1918.) 

Principles of mechanics of materials including timber, stone, cement, 
metals, etc. Constitution of iron and steel and the properties of metal 
products, including malleable cast iron. 840 pages, illustrated. 



Machinability of Malleable Cast Iron. 

A discussion of the paper by Messrs. Smith and Barr (A. F. A. Vol. 
XXVIII, p. 330), covering threading tests and data on cutting 
speeds. 1700 words. Transactions, A. F. A., Vol. XXVIII, p. 338. 

Relation Between Machining Qualities of Malleable Castings and Physical 
Tests, by Edwin K. Smith and William Barr. 

A discussion of the effect of higher physical properties of malleable 
upon its machinability, based on the results of tests and replies to a 



Selected Bibliography 401 

questionnaire. 2100 words, 2 drawings and 5 tables. Transactions, 
A. F. A., Vol. XXVIII, p. 330. 

Some Physical Constants of American Malleable Cast Iron, by H. A. 
Schwartz. 

A review of the properties of malleable with detailed data and 
charts showing the behavior of the metal under various stresses and 
physical conditions. 5000 words, 12 diagrams. Proceedings, A, S. T. 
M., Vol. XIX, Part II, p. 248. 

Physical Properties of American Malleable Cast Iron, by W. R. Bean. 
A discussion of the strength, elongation, resistance to bending, hard- 
ness, machinability, density, etc., of malleable. 2400 words, 3 illus- 
trations, 3 tables. Proceedings, A. S. T. M., Vol. XIX Part II, p. 
266. 

Testing Hardness of Malleable, by Enrique Touceda. 

The author explains why hardness tests are inadequate as a measure 
of machinability. 1000 words, 2 illustrations. Proceedings, A. S. T. 
M., Vol. XIX; Part II, p. 273. 

Effect of Machining and of Cross Section on the Tensile Properties of 
Malleable Cast Iron, by H. A. Schwartz. 

A description of tests made to determine the effect of decarbonization, 
grain structure, area of cross section, rate of cooling, shrinkage, etc., 
on the relative strength of a specimen. The results are discussed and 
conclusions drawn. 2400 words, 6 diagrams. Proceedings, A. S. T. 
M., Vol. XX ; Part II, p. 70. 

Standard Specifications for Malleable Castings (A 47-19). 

The standard specifications adopted in 1919 by the American Society 
for Testing Materials. 800 words, 1 illustration. A. S. T. M. 
Standards, 1921, p. 354. 

Some Needs of the Malleable Iron Industry, by W. P. Putnam. 

The author explains that research must be extended and equipment 
improved before malleable practice attains a high standard of 'excel- 
lence. 1500 words. Transactions, A. F. A., Vol. XXVIII, p. 257. 

Malleable Iron as a Material for Engineering Construction, by H. A. 
Schwartz. 

A review of certain objections to malleable held by engineers in 1918, 
followed by a brief outline of the malleable process, a detailed account 
of metallurgical principles involved, and a description of the actual 
properties of malleable as an engineering material. 7500 words, 15 
illustrations. Transactions, A. F. A., Vol. XXVII, p. 373. 

Malleable Iron and Its Uses, by Henry F. Pope. 

A brief outline of the characteristics of malleable and its principal 
applications as an engineering material. 1500 words. Year Book, 
A. I. and S. I., 1917, p. 353. 

Remarks on the Strength and Ductility of Malleable Cast Iron After the 



402 Selected Bibliography 



Skin Has Been Removed, by Enrique Touceda. 

An expose of the fallacy that after the skin of a malleable casting 
has been removed, the remaining metal is of inferior quality. 4000 
words, 3 illustrations. Transactions, A. F. A., Vol. XXIII, p. 440. 

Chemical and Physical Properties of Malleable Iron, by W. P. Putnam. 
The annealing process is discussed and charts are shown to empha- 
.size the importance of closely controlling annealing temperatures. 500 
words, 5 charts, 2 tables, 4 micrographs. Transactions, A. F. A., Vol. 
20, p. 363. 

The Physical Properties of Malleable Castings as Influenced by the 
Process of Manufacture, by Richard Moldenke. 

An argument for the adoption of standard specifications for malleable, 
particularly to control time of annealing, 1100 words, Proceedings, 
A. S. T. M., Vol. 3, p. 204. 

Physical Constants for Malleable Cast Iron by H. A. Schwartz. 

Results of tests on the physical properties of malleable. Foundry, 
Vol. 47, p. 462. 

Properties of Malleable Cast Iron, by H. A. Schwartz. 

An outline of the mechanical, thermal and electrical properties of 
American malleable. Engineering Nezvs-Record, Vol. 83, p. 132. 

The Use to Which Malleable Iron Castings Can Be Applied in Car 
Construction, by Frank J. Lanahan. 

A historical sketch covering the types of castings used in construc- 
tion of American railroad cars, followed by a discussion of the 
merits of malleable castings for this work. 3200 words. Transac- 
tions, A. F. A., Vol. XXV, p. 489. 

Advantages of Malleable Iron Versus Steel for Agricultural Castings, 
by P. A. Paulson. 

An explanation of the increased use (in 1918) of malleable castings 
in agricultural machinery, with reference to the tensile strength of 
malleable, uniformity of metal, and ratio of elastic limit to the 
tensile strength. 1200 words. Transactions, A. F. A., Vol. XXVII, 
p. 425. 

The Integrity of the Casting, by Enrique Touceda. 

A discussion of the value of tests to determine the properties of 
malleable, with comments on the production of sound castings. 2400 
words. Transactions, A. F. A., Vol. XXVII, p. 438. 

Effect of Machining and of Cross-Section on the Tensile Properties of 
Malleable Cast Iron, by H. A. Schwartz. 

A study of tensile properties of malleable. Proceedings, American 
Society for Testing Materials, Vol. 20 (1921), p. 70-79. 

Tests for Hardness, by T. Turner. 

An investigation to compare results obtained by Turner, Shore, Brinell 
and Keep methods. Engineering, Vol. 87 (1909), p. 835. 



INDEX 

Agricultural implements, applications of malleable for 37 

Air Furnace: 

Action of flame in 141 

Amount of air required for combustion 145 

Analysis of slag in 147 

Chemical changes in melting in 146 

Chemistry of combustion in 146 

Coal consumption of 144 

Consumption of refractories 147 

Depth of metal in 143 

Design of 125, 136 

Dimensions of 143 

Heat balance of 153 

Historical notes on early 135 

Method of firing and melting in *. 138 

Rate of melting in 157 

Roof construction of 141 

Use of forced draft 154 

Use of pulverized coal in - 154 

Temperature of metal in 152 

Variation in composition at different periods of heat in 150 

Alexander 46 

American Malleable Castings Association: 

Research work of 31, 35 

Tensile properties of specimens submitted by members of 291 

American Malleable Castings Co 19 

American Radiator Co 21 

American Society for Testing Materials: 

Adoption of specifications for malleable 36 

Specifications for malleable castings 274, 276 

Annealing: 

Changes of metallographic composition of white iron during.... 69 

Cycle, length of 218 

Effect of type of packing for 228 

Factors affecting the rate of cooling during 220 

Factors affecting height of, stacks of pots 192 

Function of packing in 190 



404 Index , 

Annealing : 

Furnace, consumption of coal in 203 

Furnace, description and use of pit type of 199 

Furnace, design of 194 

Furnace, disposition of heat in 205 

Furnace, economy of large 195 

Furnace, electric heating arrangement suggested by Touceda 

for use in 208 

Furnace, heat requirements of 204 

Furnace, pyrometer equipment for 209, 210 

Furnace, thermal efficiency of 206 

Furnace, use of powdered coal for 196 

Limitations on minimum time of 221 

Metallurgy of 61, 230 

Method of packing castings for 190 

Objections to high temperature at beginning of 214 

Operations, outline of 81 

Pots, construction of 193 

Pots, life of 192 

Pots, separator plate for 193 

Practice, early conception of 189 

Principles of 213 

Range of temperatures in 189 

Safe maximum temperature for 215 

Temperature, controlling 209 

Archer, R. S 33, 46, 63, 65, 349 

Ash, analysis of, of suitable coal for melting 115 

Austenite, definition of 41 

Austin 51 

Automotive industry, use of malleable in 38 

Barlow, J. H., successor of Boyden 16 

Barr, William - 330, 331, 334 

Bauer, 231 

Bean, W. R ' 30, 32, 263, 273, 295 

Beams, strength of malleable castings when used as 307 

Beckett, James 29 

Beilby 349 

Belgium, production of malleable in 40 

Benedick's diagram 47, 51 



Index 405 



Bessemer process, effect of discovery of 6 

Bibliography 385 

Black heart malleable, discovery of, by Boyden 11 

Blast furnace: 

Pig iron first made in, in Germany 4 

Probable facts surrounding introduction of first, in prehistoric 

period 3 

Blast furnaces, location of, making malleable pig iron 96 

Boyden: 

As a metallurgist 26 

Extracts from diary kept by 11 

Foundry career of 15 

Statue of, erected by citizens of Newark, N. J. . 12 

Successors of 16 

Boyden, Seth 95, 197 

Bourcoud, A. E 231 

Brick: 

Analysis of burnt 131 

Manufacture of fire 131 

Bridgeport Malleable Iron Co. 18 

Brinell method of measuring hardness '. . 324 

Brittleness, tests by Humphrey on 322 

Building requirements, comparison of, for gray iron and malleable 

plants .- 83 

Campbell, H. H 182 

Canada, production of malleable in 39 

Capacity of malleable plants in United States 84 

Carbon: 

Conversion of combined, into temper 66,67 

Definition of temper r 41 

Effect of, on tensile properties of malleable 292 

Graphite and temper, in graphitization 52 

Methods of determining, content 270 

Migration of, during annealing process 222, 224 

Recombination of, in pig iron, under melting conditions 137, 139 

Relation between silicon and, in malleable 55, 68 

Solubility of 65 

Study of quantitative effect of, by author in 1904 30 

Cast iron, first production of, in early stack or blast furnace 4 



406 Index 

Cementite, definition of 41 

Cesaro 46, 235 

Charpy 33 

Chicago Malleable Iron Co 19, 94 

Chrome 269 

Clay: 

Analysis of raw refractory. 131 

Location of deposits of refractory 126, 127, 129 

Use of refractory, in malleable industry 127, 129 

Cleaning castings, methods of 249 

Cleveland Malleable Iron Co 19 

Coal: 

Analysis of melting 113 

Consumption of, in annealing 203 

Consumption of, in air furnace melting 144 

Distribution of sources of 109, 1 10 

Factors to be considered in selecting, for melting 113 

Grades of, used in malleable foundries Ill 

Method of preparing pulverized 117 

Precautions to be taken in transporting pulverized 117 

Requirements in, for pulverizing 115 

Size of, for air furnace fuel 115 

Use of pulverized, in air furnace melting 154 

Coke, use of, in making malleable in cupola 121 

Color method, unreliability of, for determining carbon and silicon 267 

Columns, strength of malleable cast 305 

Combustion, discussion of, in air furnace 145 

Compression, behavior of malleable under 303, 304 

Contraction : 

Effect of size and shape of casting on, of metal 242 

Use of terms "fluid," and "solid" 237 

Converter, type of, used in triplex process 167 

Coonley, John C 19 

Corrosion of malleable - 376 

Cort, invention of puddling, furnace by 6 

Cross bending: 

Behavior of malleable under cyclic 357, 358 

Results of tests on, of malleable 309 

Stresses in, of malleable 307 



Index 407 



Crum-Grzimailo 141 

Cupola: 

Control of metal in, melting 175 

Metallurgy of melting in 163, 177 

Ratio of metal to fuel in 177 

Cutting hardness, method of measuring 327 

Dalby : .355 

Davenport, E. S 273 

Dayton Malleable Iron Co .' 19 

Decarburization: 

Control of, in annealing 226 

Extent of, during annealing process 224 

Definitions of entities in alloys of iron and steel 41 

Density of malleable 384 

Design, factors to be considered in, of malleable castings 243 

Devlin, Thomas 17, 28 

Diller, H. E 29 

Dolomite, use of, in malleable industry 133 

Dressier-type tunnel kiln for annealing 202, 206 

Drill tests, conclusions drawn from, of malleable 331, 332 

Dyer, C. D 138 

Eastern Malleable Iron Co 18 

Eberhard Mfg. Co 21 

Elastic Limit: 

Definition of 287 

Increase in, of malleable by plastic deformation 356 

Electric Furnace: 

Chemical advantages of 160 

Chemical reactions in 164 

Description of, used in triplex furnace 163 

Distribution of metalloids in 171 

Use of, in malleable industry 160 

Electrical properties of malleable 371 

Electrical resistance of malleable, effect of temperature on 376, 377 

Elongation, effect of, on resistance of malleable to dynamic ten- 
sile loads 319 

England, production of malleable in 39 

Equilibrium diagram for iron carbon system 47, 48, 49, 63 



408 Index 

Equipment, principal, used in malleable foundries 73 

Expansion of malleable 378, 379 

Fairchild 209 

Fatigue, resistance of malleable to 323 

Feeders, use of, in molding malleable castings 245 

Ferrite, definition of 41 

Ferromanganese, use of, in making malleable 105 

Ferrosilicon, use of, in making malleable 107 

Fire brick, manufacture of 131 

Foote 209 

Forbes, Alexander Duncan 18 

Forbes, Duncan 18, 28 

Forquignon 33 

Fort Pitt Malleable Iron Co 183 

Foundries : 

Distribution of malleable, in United States ....20,23 

Number of malleable, in the United States 24 

Range in size and capacity of malleable 71 

Fracture : 

Interpreting appearance of 148, 149, 150 

Normal, of malleable iron 279 

France, production of malleable in 40 

Freezing, changes of metallographic composition of white iron 

during , 69 

Friction, resistance of malleable to 336 

Fryer, J. H 193 

Fuel, classification of, used in making malleable 109 

Fulton, A. M 182 

Furnace, primitive iron, used by early Egyptians 2, 3 

Furnace, shoveling, built by Seth Boyden 197 

Galvanizing, method of hot, of malleable 263 

Gas: 

Analysis and properties of, for melting purposes 119 

Composition of producer 119 

Location of producing fields of natural 110 

Gailly, Raymond 40 

Gates, proper use of, in molding malleable 245 

General Electric Co. , 21 



Index 409 

Goecke ** 

Gontermann . . ; 52, 234 

Goodlet, James 95 

Gordon 51 

Graphite, definition of 41 

Graphitization: 

Effect of chemical composition on 52 

Relation of time and temperature in 68 

Research on, by Storey 33 

Theory advanced by Honda and Murakami 35 

Theory of 61 

Grenet 33 

Grinding, precautions to be taken in disk, of malleable castings.. 254 

Grinding as a method of removing gates, fins, etc 253 

Hammer, Alfred E 27, 29, 30, 34, 97 

Harding, Warren G 19 

Hardness: 

Method of measuring cutting 328 

Methods of measuring 324 

Relation of Brinell and Shore, numbers 326 

Relation of, to completeness of anneal 326 

Relation of, to wear of malleable 324 

Significance of cutting, of malleable 327 

Harness, early application of malleable for, parts 36 

Harrison 209 

Haswell, John 18 

Hatfield, W. H 10, 33 

Heat balance of triplex process 171, 172, 173 

Heat, disposition of, in annealing furnace 205 

Heat treatment of malleable at temperatures below critical point.. 264 

Herbert 328, 329 

Heyn, E 33 

Highriter, H. W 137, 273 

Hird 52 

Honda, Kotaro 35 

Hoosick Malleable Iron Works 17, 18 

Horsley, Sidney 18 

Howe, H. M 33, 49, 63 

Iljin 33 



410 Index 

Impact: 

Effect of, on malleable 315 

Machines for testing 322 

Testing malleable for, by series of equal or increasing blows.. 363 

Testing malleable for resistance to 316, 317 

Inspecting, methods of, malleable 267 

Inspecting, factors to be considered in, malleable for acceptance 

by consumer 283 

International Harvester Co 21 

Iron and steel in us'e at time of American civil war, review of 

types of 6 

Iron-carbon alloys, theories on 46 

Iron-carbon diagram 47, 48, 49, 51, 63, 66 

Ironton Malleable Iron Co % 19 

Japan, production of malleable in 40 

Jeffries, Zay 46, 349 

Johnson, Isaac ; 17 

Johnson, J. B., Jr 101 

Kawahigashi, Commander 40 

Kingsland, G. H ' , 197 

Kranz, W. G 160 

Labor, division of, in typical malleable plant 84 

Labor, types of, available in various foundry centers of the United 

States 87 

Laboratory, A. E. Hammer establishes first chemical, in American 

malleable industry 27 

Laboratory, McConway & Torley establish 29 

LaMarche, Charles L 21 

Lanahan, Frank J 182 

Link-Belt Co 21 

Load-deformation curves for malleable under plastic deforma- 
tion 364, 367, 368 

Loeb, Peter 19 

Machineabilit}', investigations on, of malleable 328 

Machining: 

Factors contributing to, difficulties 256 

Factors governing, of malleable castings 254 

Properties of malleable 330, 331 



Index 411 

Magnesia, use of, as refractory in malleable industry 133 

Magnetic properties of malleable 374, 375 

Magnetization of 'malleable 373 

Malleable: 

Contraction from pattern size 240 

Discovery of black heart, by Boyden in 1826 11 

Early uses of 36 

Industry, extent of, in Europe 10 

Industry in Europe resulting from Reaumur's discovery 9 

Industry, number of foundries in United 'States 24 

Industry, present extent and distribution of foundries in 20, 23 

Iron, first described by Reaumur in 1772 9 

Location and distribution of principal sellers of, in United 

States 22, 23 

Metallurgical characteristics of 46 

Misconceptions regarding 31 

Pig iron, guarantees of analyses of 103 

Production of, in foreign countries 39, 40 

Production of, in United States 23, 24 

Scrap, description of grades of 91 

Use of, for electrical apparatus 371 

Uses of, in war 38 

Manganese, method of determining, consent 270 

Manganese sulphide, effect of 57 

Martensite, definition of 41 

Material, amount handled to produce one ton of castings 85 

Material, raw, used in malleable foundry 73 

Matsubara 230, 231 

McConway & Torley, establish laboratory 29 

Melting operations, outline of . 77 

Melting stock used in making malleable 91 

Merica, P. D 33, 63 

Metallography, employment of, for testing malleable 273 

Metallography, method of polishing specimens for 273 

Metallurgy, brief history of contributions to, of malleable 33 

Metallurgy, role of, in development of American malleable industry 26 

Metals used by prehistoric metallurgists 1 

Meteoric iron discovered by Admiral Peary 1 

Microstructure of malleable 59, 63 

Moldenke, Dr. Richard . .29, 30, 32, 97, 138 



412 Index 

Molding, comparison of considerations in, of gray iron and mal- 
leable castings 233 

Molding machines, types used for malleable castings 247 

Molding methods, improvements in 247 

Molding sands, location of beds of, in United States 124, 126 

Muffle furnace, description of, for annealing 199, 200, 201 

Murakami, T ' 35 

Mystery in malleable industry 26 

National Malleable Castings Co 19, 29, 95 

New Jersey Malleable Works 17 

Newbold, Charles -....' 19 

Nichols, W. S 17 

Nicholson 328 

Northern Malleable Iron Co 18 

Nutting 351, 353 

Oil: 

Location of supplies in the United States 110 

Use of, for melting and annealing 123 

Use of fuel, in open-hearth furnace 187 

Open-Hearth Furnace: 

Advantages and disadvantages of melting in ' 177 

Design of 179, 180, 181 

Effect of invention of, by Siemens 6 

Heat balance of melting in 185, 186 

Labor required to operate 187 

Losses in melting in 184 

Metallurgy of 183 

Ordnance, applications of malleable for 38 

Ore, analysis of, used for malleable 103 

Ore, location of fields supplying, for malleable industry 96, 101 

Operations, sequence of, in malleable foundries 77, 83 

Organization of malleable foundry 72, 73 

Otis, Frank J 18 

Oxidation, effect of, during annealing 68 

Packing: 

Analyses of various types of, for annealing 229 

Composition of, used for annealing 228 

For annealing, metallurgical effect of use of 227 



Index 413 

Patterns for malleable, factors to be considered in making 241 

Payne .. . . , 51 

Pearlite, definition of 41 

Permeability of malleable 372, 373 

Personnel of malleable foundry organization 73 

Peterson 235 

Phosphorus, effect of, in malleable 59 

Phosphorus, method of determining, content 270 

Pig Iron: 

Discussion of merits of coke and charcoal 97 

First made in blast furnace in Germany in 1311 : 4 

Grades of, used in making malleable 95 

Guarantees of analyses of malleable 103 

Location of furnaces making malleable 96 

Tendency toward change in sulphur and phosphorus content of 105 

Pipe fitting, use of malleable for 37 

Plastic Deformation: 

Action of specimen under test for 360 

Behavior of malleable when tested for 340 

Change of structure of malleable when deformed under 342 

Destroying effect of, by heat treatment 345 

Effect of, on elastic limit ._ 356 

Effect of, on grain structure of 343 

Mechanical effects of 349,351 

Theory of 339 

Pope, Alfred A 19, 27, 29, 30, 34 

Press fitting, method of, malleable 257 

Production of malleable in foreign countries. . , 39 

Production of malleable in United States by states 23, 24 

Production of steel and malleable castings compared 24 

Proportional limit, definition of 287 

Protecting coatings, comparative value of galvanizing, sherardizing 

and electrogalvanizing 262 

Protective coatings, methods of applying, .to malleable 262 

Puddling furnace, effect of invention of, by Cort 6 

Pulverized coal, use of, in annealing ovens 196 

Pyrometers for annealing furnaces 209, 210 

Railroad, application of malleable for, rolling stock 36 

Reaumur, malleable cast iron described by 9 



414 Index 

Reduction in area, relation of, to diameter of tensile test specimen 298 

Refractories, consumption of, in air furnace melting 147 

Refractories, use of, in malleable industry 127, 129 

Remy, Marcel 40 

Roberts-Austin diagram 46 

Rockford Malleable Iron Works 19 

Ruff 33 

Ruer, R 33 

Sand: 

Properties of molding 124 

Selection of core and molding, for malleable 245 

Tests for molding. . 127 

Schenk 230, 231 

Scrap, kinds of, used in making malleable 91 

Shear, behavior of malleable when subjected to 310 

Shore method of measuring hardness 325 

Shrinkage, allowance for, in malleable 239 

Shrinkage, use of term in molding and patternmaking 237 

Shrinks, methods of avoiding 243 

Siemens, effect of development of open-hearth furnace by 6 

Silicon: 

Influence of, on graphitization 53 

Method of determining, content 270 

Range of, best suited to foundry requirements 54 

Relation between carbon and, in malleable 55, 68 

Smith, Edwin K 330, 331, 334 

Sorbite, definition of . . , 41 

Specific heat of malleable 381 

Sprue, use of, as melting charge 94 

Steel scrap, selection of, for charging melting furnace 94 

Steel, use of "blister" or cementation, in early centuries 5 

Steinmetz, Charles P 374 

Storey, Oliver 33 

Straightening, methods of, malleable castings 261 

Sulphur,, influence of, in malleable 57 

Sulphur, method of determining, content 270 

Taylor, F. W 328, 329 

Temperature: 

Effect of, on dimensions of malleable 378 



Index 415 

Temperature : 

Influence of, on graphitization 65 

Pouring, for malleable 235 

Use of malleable under high 378 

Tensile properties of malleable, effect of temperature on 382 

Tensile strength: 

Calculating safe, for threaded malleable 301 

Effect of carbon on, of malleable 292 

Effect of cross sectional area of specimen on 295, 297 

Relation of, of cast and machined specimens 295, 296 

Tension : 

Applying alternate, stress to malleable 356 

Behavior of malleable iron under 290 

Behavior of metals under 288 

Stress-strain diagram of malleable under successive increas- 
ing 354, 355 

Test, dynamic, for malleable developed by B. J. Walker 321 

Test lugs, preparation of 277 

Testing machines, types of impact 322 

Thermal conductivity of malleable 379, 380, 383,384 

Thermo-couples, use of, in annealing furnaces 210 

Thompson, G. H 18 

Thrasher 68 

Time element in graphitization 68 

Timken Roller Bearing Co., foundry of 19 

Tool failures, causes of, in machining malleable 335 

Torsion and tension, effect on malleable of combined 362 

Torsion, behavior of malleable when subjected to 311, 312, 313 

Touceda, Enrique 29, 31, 32, 153, 208 

Triplex Process: 

Description of 161 

Developed by W. G. Kranz .' 160 

Heat efficiency of 174 

Metallurgy of 162 

Metallurgy of slag in 170 

Troosite, definition of 41 

Tunnel-kiln, Dressier, for annealing. 202, 206 

Turner, Thomas 40, 237, 327 

Tuttle, B. B. . 18 



416 Index 

University of Illinois 328 

Walker, B. J 29, 34, 196, 321 

Wear, relation of hardness of malleable to 324 

Welding, factors to be considered in, malleable castings 251 

Welding, suggestions to user of malleable castings on 260 

White, A. E 33, 63 

White cast iron, changes of metallographic composition during 

freezing and annealing . . .' 69 

White cast iron, freezing of . 49 

White heart malleable, early production of, in United States 10 

Whittemore, J. H ' ....17, 18, 19 

Wilmington Malleable Iron Works 197 

Wood Harvester Co., Walter 18 

Wood Mowing & Reaping Machine Co., Walter 18, 29 

Wood, Walter ? 17, 28 

Woody, W. L 240 

Woodworking tools, impression malleable is widely used for 38 

Wrought iron, early use of, in making malleable 95 

Wust 235 

Yield point, definition of 287 



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